With only the slightest disparity between each tier group, and based on the realistic disadvantage of execution barriers:
S: Viola
A: aPatroklos, Pyrrha, Pyrrha O, Cervantes, Mitsurugi, Patroklos, Natsu,
B: Algol, Hilde, Aeon, Yoshimitsu, Voldo
C: Nightmare, Xiba, Ezio, Siegfried, Astaroth, Tira
D: Raphael, Leixia, Ivy, Maxi, Z.W.E.I, Dampierre
With unlikely and unrealistically perfect execution, aPat, Yoshimitsu, Hilde, Maxi, Ivy, and Pat could go up a tier.
aPat is still top with moderate execution, but with perfect execution, his maximum JG punish, whiff punish, and 50/50 damage go through the roof, easily putting him on Viola's level.
Yoshimitsu's iMCF, done at perfect timing, limits every characters options heavily to the point where they can't continue offense without have to commit to shut it down. You need high advantage or specific moves that outrange but don't move the character close to him to beat it out.
Hilde, probably the most difficult character, is capable of very high damage with proper combo execution. The skill ceiling of managing her charges effectively, having the right charges levels at the right times, is also so high it doesn't make sense to consider it in a tier list like this one.
Maxi's B+K JF series plugs a giant hole in his game, whiff punishing.
Ivy's CS completes her character, but a similarly on-point opponent will break CS, which is partly why I put her so low in the first place.
Patroklos's A+B:A+B glitch is a pseudo-JF with a 2 frame window. At i30, it does half health or more. It makes most mids very risky to use at advantage, but it can also be used as a whiff punisher for big moves and as a guard crush followup. It can be ducked on reaction and punished heavily, but 130+ damage meterless can't be ignored. Certain characters get picked up by 1B BE, too, so damage can get to Viola levels.