Did Laharl have something like that (I think there is a path where he fights Flonne)
Disgaea 1 spoilers, yay!
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There's an ending where he kills Hoggmeister, which prompts Flonne to declare that he's evil and attempt to kill him. We never see the fight or its outcome.
Defeat the Dark Assembly 100 times and everything is destroyed with Laharl vanishing, never to be seen again.
He can also ditch the main plotline to go take over Earth as vengeance for them attacking the Netherworld.
And as mentioned if you beat him in Disgaea 2, he gets angry and destroys the entire planet to kill you. Nuking planets for petty vengeance is worse than most characters here.
They're all non-canon though and make up a rather small portion of the games. The alternate endings are not the most memorable, nor particularly long. Revya has an entire Devourlord path where she [Player chooses gender, officially female in future appearances/references] goes through the entire game being pure evil; non-canon, but it's almost half the game so it's hard to argue that it isn't important or memorable and she has a unique title to differentiate that path from the official one. The Disgaea endings are a few sentences which are fairly out-of-character for the personalities shown throughout the rest of the game.
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yay
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In this world which will someday fall to ruin...
...dreams and hopes don't matter at all.