Bobo

Not A Hero And Fan 
In the original Wario Land, Bobo attempts to hurt Wario by releasing Watches from his mouth or using his giant, clawed feet and sharp fangs inside his beak. To defeat him, Wario has to use the Watches to propel himself high enough to be able to jump on Bobo's head. It takes three to six jumps to defeat him. Alternatively, Wario can use the Dragon Pot power to blast Bobo's head.
In Wario Land II, Bobo is considerably smaller than in his original appearance. He only attacks Wario directly in this game by repeatedly swooping down and flying back up again in patterns that change as the battle progresses. Bobo is also able to make wind come up from the ground by flapping his wings, making Wario fly upwards and forcing him back to an earlier section of the boss level unless he crouches. He can be defeated by jumping on him six times. Every two hits, his attack pattern changes. First it is a large and slow curve, then it's in the shape of a w, and finally it is in three lines with 90 degree sharp turns. In addition, every two hits forces Wario to stay crouched longer.