Guacamelee!/YMMV

Anticlimax Boss: Once you figure out his attacks, the final boss, Carlos Calaca, isn't very hard at all. His first form doesn't really make any effort to fight you, instead warping in somewhere, doing one attack, and giving you a few seconds to break his shield and get a bit of damage in on him. His second form is gigantic and can do a good amount of damage, but only has four attacks and each one has extremely obvious tells. This is especially true on hard mode, where every other boss has a lengthy, badass fight - especially Jaguar Javier, fought just a bit before Calaca, whose fight is a lengthy test of pure skill.
Ensemble Darkhorse: Jaguar Javier. One part Final-Exam Boss one part Best Boss Ever. The fact that he's a Noble Demon is the icing on the cake.
Evil is Sexy: X'Tabay.
Game-Breaker: Goat Climb lets you run up sheer walls indefinitely. Goat Fly lets you launch off a wall and fly horizontally until you hit another wall (even if the next wall is dozens of screens away). Together, they completely trivialize 90% of the platforming in the game.
- Collecting every mask piece in the game (aside from the one given to you for beating the Final Boss) gives you an infinite jump when in Pollo form, which breaks the platforming even harder.
Goddamned Bats: Chupacabras love to hover just a little bit too far from your attacks and spit shots which can easily catch you off guard in more hectic combats. They become Demonic Spiders quite easily in Hard Mode, or in El Infierno's combat challenges where they will wreck your combo with those shots.