Malware (Ben 10 UAF)

A vicious space-faring brigand, Vilgax is an oversized and ever-changing genetic amalgam of predatory species, who leads an army of bounty hunter and robots to wage war on any unfortunate being that gets in his way. His engineered DNA is cybernetically enchanced and is serviced by army of advanced androids. Vilgax's form is always in a constant state of upgrade. Known throughout the universe as "the conqurer of 10 worlds," Vilgax has defeated some of the galaxy's mightiest heroes, to absorb their power to become even more dangerous and get his vengeance against his nemesis Ben 10.

Description
''"Vilgax is Ben's arch nemesis that is a Chimera Sui Generis, which are large aliens with incredible strength. He controls an army of robotic minions and bounty hunters as well as severl of Ben's old villains who also seek the Omnitrix and revenge." ''

Ben 10 Ultimate Alien Force
He is one of main villains.