Vilgax

Vilgax is an intergalactic demonic alien planet conqueror, a                         Chimera Sui Generis who serves as Ben's archenemyand is the most recurring villain in the on-goingfranchise. He was introduced in And Then There Were 10, and has since appeared in all the seasons of theoriginal series (however, the only season 3 episode heappeared in was Ben 10,000), as well as season 3 ofAlien Force, Ultimate Alien, and Omniverse. Vilgax is the main antagonist of the original series.