Final Fantasy X - Adventures in the aftergame. This post turned out long and rambly but maybe some people will find it interesting!
Some background here; I've done the FFX aftergame once before, waaay back, with the basic NTSC version of course. My basic strategy was to throw aeons at all the superbosses. Turns out that if Yuna's stats are respectable (I'm talking like ~100 in the key ones here), there's very little that won't fall either to an Anima twinked out with every relevant ability (healing, draining, all the support magic, etc.) or the Magus Sisters. When I wasn't relying on them I mostly used Auto-Phoenix, an extremely cheesy ability that largely lets you laugh off singletarget attacks. Nemesis was still an engaging, tough fight, because he had the stats to outlast all this cheese until I executed a strategy involving Auto-Life, Auto-Phoenix, and summoning on turns where there's a non-zero chance he might use MT OHKO twice in a row.
But a decade and a half later, I'm playing the aftergame again because I finally have a version of the game where I can fight the Dark Aeons and Penance, nine bosses who weren't in the original version of the game. And in order to have a different experience than last time, I'm trying not to use aeons against the superbosses, or Auto-Phoenix at all.
After I beat the game, I relaxed the original rules of my challenge and started building everyone more intelligently. My first order of business was grabbing some celestials (Yuna's, Auron's, Kimahri's, and Lulu's) some capturing and the Omega Ruins, where I did a lot of levelling. The Ruins themselves are mostly a matter of keeping someone with First Strike in your frontline before each battle (else you might get ambushed by a Great Marlboro and eat horrific statusy death), and knowing the both of the dungeon's giant multi-status-hell enemies are vulnerable to Provoke. Oh and there are Demonoliths who literally have 100% MT petrify FFX why do you think this is a good idea. No status stops it, Stoneproof and/or aeons to the rescue, fortunately Yuna and Auron have the former from maingame armours. There are two bosses here, Ultima Weapon and Omega Weapon. Ultima Weapon is a joke, less HP than Yunalesca unscaled are you kidding me. Omega Weapon was just as bad in the original version, here he has a million HP and needs to be taken seriously at least, but still isn't too bad.
Next, I do more monster capturing, enough to unlock the Dark Matters gained from capturing 5 of everything, which lets me craft a pseudo-celestial for Wakka: Break Damage Limit, Piercing (many superbosses have armour), Triple Overdrive, and One MP Cost. I also do a couple blitzball games to get him Attack Reels. Since Wakka has been consistently highest-stat characters since the end of the run this proves very helpful.
After that we get to the arena bosses! The first two sets, the area and species creations, are largely manageable at this point. Noteworthy fights include Marlboro Menace, who made me customize Confuseproof for everyone (and also cast Shell because his Bad Breath does magic damage); Fenrir, an evasive and super-fast asshole who again made me bring out confuseproof, and also Kimahri's Evade and Counter for stopping one of his attacks; Jumbo Flan, who is immune to physicals but can be defeated by a combination of Slow and refleced doublecasts, with Shell/Focus to survive his Ultima; Tanket, who quick hits like made below half health and also inflicts berserk, Sentinel from someone with Berserkproof (buffed with Protect/Cheer of course) goes a long way though; and Fafnir, whose quick-hit Triple attack (two physicals and an elemental breath all of which do 2HKO) made me reach for some combination of Protect, Auto-Life, and Nuls to stand against.
The next tier is quite a step up; it roughly includes the first four dark aeons and every original creation except Nemesis. From this point on I focus mainly on Yuna, Wakka, and Auron, levelling them via Overdrive->AP (customized onto Triple AP weapons dropped by One-Eye) on a few occasions as necessary, and feeding them stat spheres dropped by other arena bosses. I also craft all three an armour with Auto-Haste, Auto-Protect, and Def+20%, which requires some heavy bribing and more Fafnir-killing. As for the originals and early Dark Aeons themselves...
-Dark Valefor is the easiest of the bunch, though I end up raising my defence well into the 100-something range so that my highest-def character (Yuna at this point) can Sentinel to survive her physicals, which makes her easy (the overdrive is a OHKO, but whatever, Auto-Life exists).
-Earth Eater is imposing with his massive counters which OHKO me at this point, but I basically bruteforce through him after raising my strength some so at least I'm doing 99999 now.
-Greater Sphere counters almost everything with an Ultima which hits notably harder than the species creations who have it, so a bit more magic defence (One-Eye fortunately does double duty by dropping those, and is really easy) is in order to survive that.
-Shinryu is actually easy enough with that same level of magic defence; Wakka can survive his focused Shining. I buff him with Trio of 9999 and Cheer before killing off Tidus and Rikku so that Shinryu won't erase Wakka (Shinryu has unblockable 100% unrevivable petrify-shatter, but won't use it if only one person is alive), then attack while tanking his counters and making sure to heal with Trio'd potions before every turn Shinryu gets.
-Catastrophe doesn't attack very often though does some scary shit when he does (either loads of MT status or some heavy MT damage). None of it dispels though so this gameplay is super-vulnerable to Auto-Life.
-Th'uban has a counter which does solid physical damage and dispels, including Auto-Life. If your defence is real trash it MT OHKOs with no chance to revive, I remember thinking this was so cheap when I first fought him. But some modest defence boosting from fighting Tanket a few times makes this counter easily survivable. Otherwise his scariest move is Rainbow which does a bunch of status hell but none of it too reliably, so I mostly just hope it doesn't inflict confuse on all three at once. Going for a statusblocker armour is problematic because he dispels all the time, and I need Haste/Protect to deal with his counters and press my offence.
-Dark Ifrit, at my current stats, OHKOs with everything he does. He also counters with a physical. But he's all ST except for called shot overdrive and has no status tricks, and isn't super-fast, so whatever, get owned by Auto-Life scrub.
-Dark Ixion is tougher: same basic idea as Dark Ifrit, but he IS fast. My first plan is to try to tank some of what he does, but this proves a bad idea since his attacks add too much status (sleep, delay, breaks) to be worth it. So I end up dealing with this one with Auto-Life too, though it requires raising my speed via some Fenrir-killing. You then need to fight him a second time, but this form DOESN'T counter so is a joke?
-Dark Shiva is super-fast, quick hits, and might even doubleact her physical, I'm not sure. She can overwhelm Auto-Life strats with this very easily. Fortunately her HP/def aren't so hot, so a high-str (near 255 now) Wakka can take her out in two Attack Reels (Entrust an overdrive from someone else) before her bullshit can get started.
-Neslug is a puzzle of overcoming his insane regen + physical immunity, but it's a puzzle I'd solved on my first playthrough. Trio'd Gems are the answer, letting everyone deal 50k damage with fast recharge. Outside his regen phase he has some offence but nothing compared to some of the rest of this field.
-Last up, Ultima Buster. His Ultima is brutal; I need to get my magic defence to around 220 to survive it, and of course use Shell as well. Adding to the problems is he doubleacts and throws in a physical as well. I only have one PC who can survive that combination, so there's a lot of revival and recasting Shell.
Okay! That brings us to the tier of bosses who you really, really want some great stats for. Here's what I end up getting:
-255 Strength for Wakka so his Attack Reels does as much as possible. Auron ends up getting to 255 as well, Yuna a bit lower (220 or so) but she hits everything for 99999 unless she gets MP-busted anyway, so it's good enough.
-170 agility is the magic number to have the highest speed. More is "useful" for tiebreaks between PCs but PCs always win tiebreaks with enemies so who cares. As mentioned above I already got this to deal with the previous tier of foes.
-255 Defence; this is needed for Penance in particular and very helpful for some of the remaining dark aeons so I can actually survive some of what they do.
-About 220 magic defence as per above... ironically none of the remaining bosses really necessitate high magic defence anyway, they don't use magic and the biggest example tends to just OHKO anyway even at 255. Arguably the most important use of magic defence at this late stage is to survive the counters of Earth Eater and Greater Sphere more easily, and see below for what that matters!
-About 85-100 luck on both Yuna and Auron. This is super-helpful for actually hitting the remaining Dark Aeons; 86 appears to be the number which is required to always hit Penance's arms, the one fight where misses are deadly. Luck is much harder to get than other stats; you have to kill Earth Eater AND Greater Sphere [see above] since both Luck Spheres and the Fortune Spheres to activate them are rare (Attack Reels + Entrust to the rescue against their counters). Fortunately unlocking Nemesis gives you 10 Master Spheres which can be used on everything; luck spheres are by far the correct choice for them.
-Other stats don't really matter (well, you want 9999 HP but you can't not have it by now, realistically; more MP is helpful on people without One MP Cost, too) and the people who max out everything terrify me.
Also some dark aeons are heavy status users; I get everyone an armour with Stoneproof, Sleepproof, and either Darkproof or Slowproof.
So onto the bosses themselves!
Dark Bahamut - On his own turns he only uses physicals, until he charges up Megaflare which obviously you survive with Auto-Life. He counters every five attacks with Impulse which damages and inflicts MT petrify, slow (the slow ignores status immunity!), delay, and full break. This is monstrous! One way to cheese him out is to just slowly counterattack him to death yourself; counters don't trigger counters. Another way is to call aeons to block the Impulses. But cheese is boring. Block petrify and take the Impulses. The key is that
you don't care about living after being hit by Impulse. The best time to trigger them is right before Megaflare; Auto-Life and you're back with all those horrible effects gone. Recast Haste/Protect as necessary, Sentinel with Auron (to reduce Protect casts and increase counters), win.
Dark Yojimbo - My first attempt involves sticking with the statusblocker armour. I cast Protect, Yojimbo uses Wakizashi and does over 11000 to everyone. Haha okay. Go back to the tanking armour! Otherwise Yojimbo has a ST petrify attack (doesn't shatter, heal with Soft), an attack which inflicts Full Break (Dispel to the rescue), and the aforementioned Wakizashi which I survive with Def+20%. He has an overdrive but it charges up way more slowly than the others (good thing, too, since it dispels auto-life... only an aeon lets you live, not that I see one). He's actually pretty easy now! Good thing to since I have to beat him five times. He drops a Ribbon armour for Yuna which is a nice upgrade for the remaining dark aeons.
Dark Anima - Status hell. Unblockable ST death, more petrify shattering, and Mega Graviton which does doom/slow/sleep/silence/blind/curse. Sleepproof + Stoneproof is key here, cast Haste if Slow is applied (only my Auron is vulnerable, which helps), revive otherwise. Her damage actually isn't too notable, just the status, so once that's survived she's not too bad. Auto-Life against the usual overdrive.
Nemesis - Oh okay he's not a dark aeon. Anyway he's still the only superboss who can MT OHKO on consecutive turns (in theory you can survive his Ultra Spark, it just needs over 30k HP, lol forget it). Having 170 agility is an absolute 100% must (well, I've done it without before, but that involved Auto-Phoenix and many aeons against all his possible back-to-back MT OHKO moves, which mercifully are predictable), but beyond that Auto-Life can handle his offence. Oh yeah and never attack him with anything but physicals or magic.
Dark Magus Sisters (together) - You can fight all three at once. This... might be the hardest fight in the game. On turn 1 the sisters act in sequence, with the third using Delta Attack, which does 600000 (yes) damage and dispels auto-life, get wrecked. You can't even block that with most aeons since the first two sisters will kill the aeon, leaving the third to Delta Attack your poor party. Only one aeon can stand against this... your own Magus Sisters! After that, you just have to survive three max-speed enemies all of whom have ST OHKOs, with some auto-life dispelling thrown in for good measure. Ugh. Maybe someday! Fortunately there's a way to fight them one at a time.
Dark Magus Sisters (alone) - Each sister uses Mega Graviton as their (fast-charging) Overdrive, the status hell move above, so statusblocker armours come out to play. Otherwise they each have a ST OHKO move (Cindy's kills your MP, Sandy's dispels auto-life). Keeping up haste when possible is useful, of course, as is Auto-Life except against Sandy (Cindy also dispels it, but with her survivable physical; I have Auron sentinel to draw it predictably and survive it, also draws Camisade's OHKO and MP bust). They're not too bad this way. Of note, Sandy and Mindy both have ludicrous evade due to luck, especially the latter whom I can only hit with Attack Reels. I guess the fight against all three at once might be the one place where maxing your luck is actually justified.
Penance - The final showdown.
Armour is the aforementioned Auto-Haste, Auto-Protect, Def+20%, and now I add Auto-Potion, selling off all my potions except X-Potions and bribing Valahas for 99 of those. Auto-Potion means I don't die to damage unless OHKOed. Ally overdrive mode for all.
Actually Penance is really quite cool. He's got two arms, they have 500000 HP and require about 86 luck to always hit. The arms do horrifying things; petrify-shatter, Mighty Guard (regen on a 12M HP boss is... a thing), Mega-Graviton status hell, dispelling physicals... ugh. So the solution is to not let them get turns. They act every 12 clockticks, with max speed you can Quick Hit five times before they act, so two PCs capable of doing that + one GRENADE from Wakka kills them. Easy right? ... nah, they come back after a certain amount of time dead. I never figured out what that time was, probably somewhere in the 10-20 clockticks range. For reference, with max speed and Haste, a normal turn is 4 clockticks, Quick Hit is 3, and Quick Pockets/equip switching is 1. Getting a turn after auto-reviving means you don't get credit for haste, and takes 9 clockticks, which is really bad!
Penance himself 12M HP, acts every 9 clockticks (max speed without haste). For the first quarter of the battle he only uses Obliteration, an MT physical which has a base damage (against 255 def) of 23000. With Protect and Defence+20%, this is survivable. Once he loses quarter of his health, he switches to Immolation, which is ST, but 33% stronger, and inflicts Full Break and destroys MP. The key is that Cheer x4-5 lets me survive this as well. The Full Break can be dealt with using Dispel (sadly, a full-speed action; I discover to my disappointment that the Use variant, Purifying Salt, does NOT get rid of breaks). The MP damage at first is super-annoying, but eventually I lightbulb and realize that using Three Stars (MP cost = 0 for the party) is an option because with this strategy, I never actually die and lose the status. Dispel, incidentally, does not get rid of "secret statuses" including Cheer and MP-cost-zero. It also doesn't get rid of Auto-Life, which I cast just in case of emergencies.
The real problem is the arms keep coming back, and I keep having to kill them. Helping me out on offence is Wakka; he doesn't have luck or defence-ignoring to do good damage with his physicals, but Attack Reels does a number on the arms. Other PCs Entrust overdrives to him when he gets turns. Never use Attack Reels unless there's an arm present since they have lower defence and thus Attack Reels helps out more against them. Wakka's other turns are used on utility (Dispel, Quick Pockets to heal MP, Cheer, Auto-Life) or if he has nothing else to do, switching weapons to build overdrive faster. If the arms get turns, not only do they do horrible things, but in the later stages of the fight Penance can use Judgement Day on his own turn if both arms are alive, which is MT OHKO... Auto-Life lets me survive, but the lost time from the revival is hard to make up for.
On the winning run, I get into trouble early but then recover and mostly cruise until towards the end when the second arm comes back at a bad time, right before I'm able to kill the first, with Penance about to get a turn. For the first and only time in this run of the superbosses, I summon an aeon to take the resulting Judgement Day. My party returns and I kill off one arm, but an Attack Reels decides to go mostly for Penance and I'm not quite able to kill the second, which attack Wakka, petrifies him, and shatters him. I despair, this is NOT a fight where I can win with only 2/3 my normal clip of actions. But I'm so close, I focus all my efforts into doing as much damage to Penance as possible before the arms get another turn to start overwhelming me... and he falls.
Fun times. Game clock is at 91 hours now. In general the aftergame experience was enjoyable. The worst part is unquestionably monster capturing; getting 10 each of 102 enemies is a tall task, and running around in circles for the 8th, 9th, 10th copy of rare monsters like tonberries is not fun. Capturing alone probably took 10-15 hours of the 40-odd hour aftergame.
But the bosses are fun. Definitely a game you need to be willing to consult what the bosses do for the later ones because figuring out which statuses to block by brute force would be annoying, but past that the varied strategies and executing them is enjoyable. Even the "grind" aspects, besides monster capturing, are actually enjoyable enough because they're actually quite fast; the game is very much about grinding smarter, not harder (fighting the right superbosses as efficiently as possible, using the Overdrive->AP trick against Don Tonberry for levels, modifying Kottos's drops for Power/Mana/Speed Spheres, etc.) and no one part of this grind takes too long, unless you really want lots of luck, but part of the fun is figuring out you don't actually need that much.