Rudy the Clown

Rudy the Clown is the hidden true main antagonist in the Wario Land 3, a giant green-skinned clown he acted as the final boss in Wario Land 3 - where he manipulated Wario into freeing him, only to declare he had no further use for the greedy anti-hero and attempted to "squash him like a bug": following this defeat Rudy the Clown would become a recurring villain in later games.

Wario Land 3
Rudy the Clown was an evil being that arrived on a once peaceful world and attempted to take it over but was sealed away with the aid of 5 magical music-boxes, however he used the last of his power to curse the inhabitants of that world into strange monsters as punishment, during the course of the game an unseen Rudy has Wario collect these 5 music boxes to free him only to instantly betray Wario once he is free - attempting to kill him as he saw no further use for Wario. However Wario defeated the evil clown and with Rudy defeated the world he had cursed returned to normal - as thanks the people of that world allowed Wario to keep all the treasure he had found which, in Wario's view, made it a very happy ending.