Matches of note.
Jessica Albert (DQ8) vs. Lady (SH3) -
Okay, Lady probably wins this, but I remember the issue of how good Jess's Magic Burst was coming up in chat, and this is actually pretty close.
According to the stat topic.... Jess has 273 base MP. But she equips a Staff when going for MB, so make that 373. That's 746 damage. The damage average using Gigaslash (Guv doesn't have enough skill points to get to Gigagash at lvl. 40, the stat topic's level, though this is fair enough to dispute; Dragon Soul I find extremely illegal myself, as you don't even need to get it when doing the aftergame) is 176. That's 4.24 times average damage, or (using 40% = average damage) 1.7 PCHP in damage.
Lady's Malice Umbral has 7200 HP. The stat topic has 250 the one-turn average, and 289 as the three-turn average... but damage is somewhat higher in-game due to having access to Crest Magic, especially Arc Surge (1 turn for 30-36% boost in damage over 5 turns? Yes. And as noted before, Lady probably shouldn't get double-credit for Lost Progress). So... I will arbitrarily say that 360 is closer to the in-game per-person damage average (since bosses should be held against in-game PCs, not DL-legal ones.). 360*4=1440, and 7200/1440 = 5 turns of survival. Taken literally, that's 2 PCHP, plus a final tap to Lady herself.
So... it comes down to how harsh you are on boss HP, I suppose. Certainly people have punished boss HP more than a naive approach like the above gives. But Jessica does need to kill instantly - I suppose she can Kafrizzle first, then Magic Burst for around 2.2 PCHP total (Twin Dragon Lash is a bad idea, she'd lose the MP boost from the staff), but as noted, even if Jessica somehow survived Lady's first turn, she'd die from Lady's counter.
Arnaud G. Vasquez (WA4) vs. Guy (FE7)
Er... I know that some people toss movement out entirely in the DL, but if Arnaud hypothetically fought Raquel, I think it'd be pretty clear that unless Arnaud also Shut Out Raquel, Raquel could just waltz out of a Slow Down'd hex with Move+Attack. I certainly grant everyone in the DL a WA4 "take your entire turn" move command, at least, which generally isn't helpful unless you're considerably faster than Arnaud - otherwise he just recasts it, and eventually he doubles and Shuts Out as well.
Anyway. Guy is from a system where everyone inherently has Move + Attack, so, uh, yeah, I can't really see just opening with Slow Down as being particularly effective here. On the bright side for Arnaud, Shut Out itself is an instant-win when fought on a Fire Emblem battlefield - tie Guy down in a square, bombard him from afar. When fought on a WA4 battlefield... it depends on if you always let the opponent start in the center hex (which is fair enough, a good few bosses start there). If Guy doesn't start in the center, Shut Out still works. If he does... I think Arnaud still wins. Arnaud uses Slow Down on the center hex. If Guy hangs out there, then I think Arnaud can beat him thanks to repeated doubled Hi-Blasts. If Guy moves away, then Shut Out -> run run away -> uncounterable Hi-Blasts.
So yes. Shut Out hype, since both are from systems with movement and Guy is in fact noticeably hurt by the fact he can't go range 2 unlike say Lyn.
Bernadette Egan (S5) vs. Lorenta (VP1)
The polar reverse of Jessica / Lady. I doubt that even a Mystic Cross PWS can kill Bern, so Lorenta's definitely going with the turtling strategy. Okay, Lorenta just hangs out at first doing nothing to save CT. Eventually Bern will force her to use Heal, due to the risk of a Breath of Ice KO or to Silent Lake->Knives. After that, assuming Lorenta has no luck getting purple gems from her bird, she has 4 turns of recharge before she can Heal again. Right before she can Heal, Bern can Silent Lake, then switch to knives. As a note, if I understand S5 mechanics right, Bernadettes deserves no respect for being able to chain multiple Silent Lakes - she's below average speed, so Lorenta will have a chance to Heal before Bern can recast Silent Lake. This is why S3 Chris is awesome, her Silent Lake beats out nearly everyone and thus can be chained really well.
Bern's Breath of Ice does an amazing .19 PCHP damage. And she's got to Silent Lake a turn early, as noted before. So...
Turn Lorenta decides to Heal: (Heal, BoI)
T2: WR, BoI
T3: WR, BoI
T4: WR, Silent Lake
...followed by 4 turns of knives. Of which her non-critical hit does .14 PCHP damage. .58 + .56 = a mere 1.14 PCHP of damage after 8 turns.
Lorenta has only .82 PCHP, however, so it looks like Bern pulls this one out. And I suppose that Heal is only 80%, meaning that even if she hadn't, Bernadette would have enough Breath of Ice charges for another go round to finish things. Lorenta's "wait around and outheal" strategy came dangerously close to working here, though, which is scary.