I've beaten all the difficulty 1 and 2 villains, and I have to say, I'm impressed. Each of the villain decks have unique gimmick that can change the parameters of the fight. Against Apostate, the demon, you have to take out his relics, or he'll resurrect when reduced to 0 hp (and he has a lot of cards that force relics into play). The Plague Rat infects you with a disease and causes you to damage yourself (which got pretty hairy, because my team's strategy revolves heavily around Legacy's power that boosts hero damage).
But my favorite fight was probably against Spite, the transhuman serial killer. He's unique in that most of his cards are "victims," which cost you damage, cards, or other disadvantages to rescue, but which can heal him if they're in play when he draws a card that kills them. His offense is entirely wrapped up in his indestructible "drug" cards, and he has massive healing until he gets 5 such cards into play. However, if you can save enough victims, then when the time comes for him to transform, you get a big chunk of bonus damage against him.
It's just a neatly setup fight. It really feels like your team of superheroes is trying desperately to track down this drug-fueled serial killer before he strikes again, and he's constantly slipping through your clutches as his victims disappear one by one. I love games where the mechanics are part of the story.
It makes me really want to play the tabletop game again. Even leaving aside the tactile pleasure of manipulating the cards themselves (which is not something I easily discount), I have a bunch of heroes, villains, and environments that have not yet been converted into video-game form. I so want to play them all!
This, of course, is known as a "good problem to have," and I might have to make some arrangements to make it happen. If I can get together a real-life game, I'll be sure to write a special post about it. (I suppose I could just play a tabletop game by myself, but somehow that seems sad in the way that a solo video game session does not).