I don't generally like bosses in fighting games, they're usually a matter of getting obscenely lucky and having a character who can spam fast high-damage projectiles with low recovery frames. I feel like it shouldn't be a case of, "Can I finish them off before they use a super attack that will chip away most of my health, can't be dodged, is spammable, and has comes with no warning?" But that's how they always are.
The bosses I have the most disdain for are not those kinds though, the ones I really hate are the bosses who run on the same (theoretical) rules as the player. Ones that can be thrown, knocked down, hitstuned, etc. I can deal with Marie in Skullgirls, Yami in TvC and the like as much as I hate their design philosophy, what I can't deal with is:
• Al Azif ex Mortis (Nitroplus Blasterz): She's fast, she hits hard, she loves to throw refuse, she's always 4 levels above the current difficulty, her super moves are overpowered versions of regular Al Azif, she spams insanely fast energy balls that chip away as much HP as a blocked super move would, and her lethal blaze is undodgeable (it also chips away half your full health bar). At least you can throw her, but unless you're constantly in her face and hitting her, she'll stand back and zone the hell out of you until she has 3 super bars and then pop her lethal blaze to finish you off. I like going for all the achievements in my games, but with the case of "beat story mode with everyone" for this game, I'll pass!
• I-No (Guilty Gear XX Accent Core): She's a character you can normally play as, and she isn't pumped up on steroids when you fight her in story mode, but what she does have is a spammable super attack that deals tons of damage, cannot be dodged, goes all over the place, and can't be used by human players. Yep, it's one of those moves that only the computer can use, and it sucks to fight against.
Surprisingly, I don't hate Inferno in SC2, and that's mainly because he's not unbearably cheap. He's just Charade on fire, no massive difficulty spikes of moves that only the computer can use, and no unreasonable level of challenge.