If anyone's curious, I view Nergal as 36% PCHP, but with defences which cut damage by 54%/62%, for total durability of 0.78/0.95.
Nergal vs Ursula (BoF4): I think he's just durable enough for this. Surprised Ursula's damage is so low, I remember her being comparable to Ryu. Masters probably.
Nergal vs Shion: Shion will doubleturn eventually, and has MT to get around counters... but uh she doesn't have the MP for this.
Nergal vs Setzer: Nergal's definitely partially reliant on defences. It saves him from Ursula's Death to me, but also means he dies cleanly to doubled dice.
Nergal vs Scythe: Depends entirely on if Nergal OHKOs. Scythe can chip with uncounterable MT (Isolate Darkness) and has instant death if he survives an attack. I'll give Nergal the benefit of the doubt, though, sure.
Nergal vs Lich: Lich durability sucks about as bad as Nergal's, he just has better defence and paralysis... neither of which is relevant here.
Nergal vs Mystic Knight: There's an argument that Nergal doesn't explode to Holy Sword, but eh. Flavour is strong, here.
Nergal vs Malak: Malak has both good magic durability and his own damage is significantly boosted. And you don't need much of a damage boost here.
Nergal vs Avril: To Dhyer, since you're the only other voter: Avril has either best or second-best damage of the WA5 PCs due to the cast's weird issues and her having game-best atk. So yeah, this handles Nergal.
Nergal vs Bernadette: Nergal 3HKOs, so Bernadette can alternate healing and uncounterable Breath of Ice.
Nergal vs Raijin: Yep.
Nergal vs Raja: Nergal still 2HKOs even if Raja has a shield, and his res is high enough to shrug off Holy Word for a couple turns. St. Fire... I'd probably see doing damage, but not hitting a weakness, hence missing the 2HKO? Anyway Raja is so slow I think Nergal may get his second turn before Raja gets his anyway, making this all moot.
I'm assuming Rei's status has the same accuracy as Implosion (52% with her default equips). We never did test it to be sure. If her status is indeed turn 1 it flips one fight (Shion) and gives her a case against another (Malak).
Rei (SaGa) vs Ursula (BoF4): Status resistance.
Rei vs Shion: Slow into fatal damage.
Rei vs Setzer: Survives a hit.
Rei vs Scythe: Yeaaah no, Rei damage not that great.
Rei vs Lich: Lich freaking OHKOs, Rei only 3HKOs, so I don't think even Glass Shield can tilt this?
Rei vs Mystic Knight: MK is faster! That said, yikes, only by the slimmest of percentages, and is all one hit, and doesn't OHKO before buffing, and runs into Glass Shield counters thereafter.
Rei vs Malak: Sure.
Rei vs Avril: Glass Shield.
Rei vs Bernadette: Death is probably turn 3-4 here, but Rei is notably faster (6-5) and has Glass Shield. If Reaper is turn 3 she wins, but turn 4 I think she just falls short on needed JP. Bernadette is lucky her physicals are ranged! Ehh MagicWear lets Rei up her WIL slightly at a durability hit (which isn't relevant), so yeah, she takes this.
Rei vs Raijin: Glass Shield.
Rei vs Raja: Glass Shield.
Nergal 6-5
Rei 6-5
edit: Interestingly despite both having 5 losses they're to almost entirely different people. Somehow the only dueller both lose to is Malak. I blame Super.