You know what, now that you mention it I'd say it probably would be just an Environmental Destruction feat as none of the vampires ever displayed any kind of space-time warping abilities, and even when the Vampire Essence turned into a cloud monster it didn't cause any kind reality distorting effects even to those that were sucked into it's body.
I don't think Princess Bubblegum witnessed anything as the candy person in the flashback that Billy interacted with was clearly someone else, and seeing how overly cautious she is I also don't think that she would be anywhere near the fight since she knows that she'd just get in the way, so it's more likely that she got second-hand accounts of Billy's battle with The Lich and ended up coming to the wrong conclusion. And even assuming that she did witness Billy's entire fight and saw him harm The Lich with his gauntlet the fact still remains that she was wrong to assume that the Gauntlet would be capable of killing The Lich, and also never accounted for the sweater that she gave Finn being capable of killing The Lich.
DM me
My point is that she didn't consider Finn capable of hurting the Lich, which implies that Finn only destroyed him because of his weakness to the "power of love."
And what would be the justification? Feats considered environmental destruction are based on feats that only affect the environment and not the opponent, feats based on chain reactions, or feats performed over time.
Again there is nothing stating/implying that The Lich was ever physically weakened by the "power of love" so you can't use that as an argument.
To be clear regardless of whether or not the Vampire Essence would qualify for Environmental Destruction the fact would still remain that it can't be applied to the Vampire King or Marceline's physicals as 1)there is no UES for that so it doesn't automatically scale to one's physicals, 2)There is nothing stating/implying that Vampire Essence can passively boost one's physicals to that level, 3) None of the vampires have any kind of physical enhancement ability that could boost their physicals to that level, 4) The Vampire Essence itself doesn't show any kind of reality-distorting effects to it's surroundings nor does it physically distort anyone/anything that comes in contact with it, so it's questionable as to what it's method of destroying reality would even be .
Basically, OP said that the Lich and Hunson should be downgraded to 5A because the 2A feat isn't valid and the Low 2C feat isn't applicable in combat and doesn't scale to the physicals. The outcome was as follows:
Ok here's the main contention against my proposed revision:
