1. Yuna (FFX)- Duh
2. Reicher (MK2)- I don't let him spam his physical, so Holy defense can slow him a little. Just nasty if you don't block Holy or heavily resist Physicals. 2 PC HP, halves damage, massive damage onslaught
3. Elc- Fast, decent HP, halves a lot of damage (effectively 3 PDur/MDur is the halving is applicable), and Invincible to protect him from status. Under Invincible he can do 3.38 Physica Damage, 1.23 (at minimum) ITD PC HP Magic Damage (Plus more with a follow up physical up) plus more if doubles are involved MP Busting helps shut off some tactics of other PCs (And perhaps a few bosses) + Status blocking accessory. In a straight slugfest he may not even go for Invincible
4. Sephiroth (FF7)- So, need to sort him out a little. Speed Pluses are legal to me, but you won't have them maxed out. FF 7 Speed might be a little questionable anyways. I'm saying 115% effective speed for right now. He definitely doesn't OHKO. I'd taken the HP average around 8000. That's 2 maxed HP Pluses + 20% HP loss from magic items. There's no real reason not to hold these to him especially. 78% MAgic Damage, 37.5% Physical Damage (Yeah, why are you in the front row?). Great status, Wall (which could last longer than 3 turns), nulls short range option, Dispell. He has 80,000 HP. Average damage at the time. You'll have at least one PC who should be doing 11,000 ish (Yuffie/Cid/Red XIII w/ Double Cut). Typoon is 8000 and you have lowest options you'll be seeing are 5000. I would say including limits, 10K might be about the right average. This puts Sephiroth at slightly above PC HP. So 115% Speed, PC HP, anti short range, 78% Magic Damage, Plenty of Nasty Status Choices.
5. Albedo (XSs)- 1.2 PC HP, 20% Magic Res, Cuts Fire/Lightning/Ice 75%, 115% Effective Base Speed which boosts to something crazy (like 300%). His key issue is that he starts out with a 3HKO (I'm calling that 49.9% just categorically) and the nasty EP busting/Confusion comes at 50% HP (if you allow Demonic Gaze to hit bosses-potentially capping at 0.5 PC HP- Fallen Angel serves no purpose. However, I guess the reality is that anyone who OHKOs him likely does the same to Kefka, Killer and Sephiroth. This means that boosting speed->drain is really effective
6. Killer (SH3)- Prone likely allows him to open with either OHKO magic or physicals? Am I overrating it? Instant Death and Silence. Probably around 1.25 PC HP to me or something in that area. Not the sheer damage of Kefka, but a little bit more balanced and versatile (better status options), OHKO magic versus OHKO magic counters at low HP.
7. Lamington (Disgaea)- 2.3 PC HP, halves Physicals, 60% Evasion, 0.8 Ice Physical, 0.6 Physical Damage, 40% Magic. For all that he isn't a lot of tricks or going for overall or anything. The package is really solid. Someone like Kefka may have double the damage, but having 4x the physical durability feels like a trump there.
8. Kefka (FF6)- 1.46 PC HP Phys Damage, 0.64 Magic Damage, but I'm calling him likely average speed (he certainly is turn 1!). MAybe 1.2 PC HP? Something around there. 1.5 PC HP Magic DAmage if you can't OHKO him. So no solid defensive trick like some of the ones above him have, but the damage is still nasty
9. Mewtwo (PKMN)- Yeah, I guess I don't let Pokemon switch out non-ideal moves anymore so Mewtwo doesn't get Safeguard (Or...well, I guess gen 3, Mewtwo will opt to throw out Amnesia). So 2 Mdur, 1.28 Pdur (will can be massively increased), 50% Healing and 68% Magical Damage, 130% Speed
10. Citan (XG)- 58% Damage (Elemental, but unless you get all the elements, not a big deal), 157.6% Speed that he can double, 125% HP and about 50% Healing
11. Naliah (FE10)- 75% Damage, ~150% Durability, 38% Evasion. Her flaw is that despite everything, there's too much status running around despite her level of resistsance.
12. Rika (PS4)- Based on current numbers, Rika's ID is...47.7% to me. Illusion is never usable. She still has a lot of healing and can get over 100% evasion (although given some aspects of it, I do think I would see Godlike tier fights against at her consistently getting through every once in a while. All the bosses who throw out physicals ignoring this doesn't exactly make is seem like she should be beating Reicher with this). I'd call it about 75%
13. Kato (SH2)- More direct status than Altima with fewer holes and more durability
14. Gilgamesh (FF5)- Great PC Killer. I...am loathe to give much respect to the portion fo the fight where you can win via defending and healing.
15. Altima (FFT)- I gave her a 4, so...