Darkdeath Evilman

Darkdeath Evilman is the main antagonist of Zettai Hero Project: Unlosing Ranger Vs. Darkdeath Evilman, a Roguelike published by Nippon Ichi software in 2010. The game centers around a young man (named by the player), who is chosen to become the next "Unlosing Ranger" after Pirohiko, the previous Unlosing Ranger, was ran over by a car.

The meat of the game centers around the the main character training for the final encounter with Darkdeath Evilman in "Bizzaro World", a moster-filled parralel universe where the Unlosing Ranger can solve people's problems by beating up the physical manifestations of those problems. Every level completed leads to a battle with the tituliar villain, though for the most part these are simply glorified cutscenes with limited player interaction. There is a proper final boss between the main character and the Bizzaro version of Darkdeath Evilman.

Backstory
As he reveals late in the game, Darkdeath Evilman was child prodegy, who was kidnapped by an evil organization. Since nobody game to save him, he lost faith in heroes. As a result of this, he concocted a nhilistic plan where he would first kill the Superbaby, and then blow up the earth with a nuclear warhead of his design.

Luckily, the Unlosing Ranger proved inspiring enough to win over Darkdeath Evilman. The game's ending shows that he has given up his villanous was for good, and has joined up with the Unlosing Ranger and his friends (though the game still refers to him as "Darkdeath Evilman").