There should be some Character who you fight in act 1 who’s like, really difficult. Then you fight him again right before Act 6, but after act 5, and he… Goes down in two hits.
You’d fight Blackie as the Penultimate Act 5 boss, and then Trotsky shows up once he’s at half health, and they fight as one for the Final Boss of act 5.
Hyena would be a hide and seek boss, who you constantly have to be aware to get a hit on, and too long between hits would let him heal. Like, he’s over here, now he’s over there.