How do you beat the genie in Wario Land 3?

Answer 1

His name is Diablos. Draw/Cast his own Demi spells back at him, and keep summoning your Eidolons. His own gravity-based spells cannot kill you, as they do a percentage of damage to your lifepoints, the only danger is when he reduces you far enough, then uses a melee attack. But since he favours his gravity spells, it's not hard to recover if he starts getting the upperhand.

Answer 2

To defeat Genie, Wario must pick up the magic lamp and throw it. If the lamp lands right-side up, a small cloud will rise from the lamp's spout.