Tetrax
From Wikitrix
Tetrax, is a Petrosapien mercenary, hired by Vilgax in the episode "Hunted" to take the Omnitrix from Ben. He has nearly impenetrable gray armor, a black helmet with a small, green triangle (presumably for sight) on it, and carries a large rifle. His Petrosapien physiology can manifest through the armor, allowing him to use his powers without removing it.
Unlike the other hunters, Tetrax is allied against Vilgax. Upon first discovering that Ben has the Omnitrix, he laments the fact that out of the planet's six billion inhabitants it would end up on the wrist of a child. He also berates Ben's lack of strategy in regards to its use. After helping Ben to defeat the other hunters, during which Ben learns to use the Omnitrix strategically, he decides that the Omnitrix is in good hands, allowing it to remain with Ben. He also gives Ben his hoverboard, saying that it might come in handy.
Tetrax returns in Ben 10: Secrets of the Omnitrix, where his past is explained. As a being who cared about no one but himself, he became a mercenary and ended up hiring himself out to Vilgax. When he finished the job Vilgax gave him, Vilgax created a weapon and used it to destroy the Petrosapian homeworld when they would not bow down to him. This caused Tetrax to betray his former employer, and he now works to rid the galaxy of his evil. He arrives on Earth after receiving the Omnitrix's SDM (Self Destruct Mode) signal, and takes Ben aboard his ship in search of Azmuth, the creator of the Omnitrix and the only one who can deactivate the self destruct function. Unfortunately, Tetrax's problems are multiplied when Gwen stows away aboard his ship, and Ben's transformations are revealed to accelerate the countdown.
On the planet Incarcecron, Tetrax runs into Sixsix, another of the bounty hunters hired by Vilgax who ended up on the prison planet. After a brief battle, he and the Tennysons find Myaxx, Azmuth's former assistant. Because of her, Tetrax is forced to reveal that the Omnitrix's explosion could destroy the whole universe, instead of just the wearer as he told Ben. Tetrax then leads the group to Azmuth's compound on Xenon, where he faces Sixsix again twice before defeating him. After Vilgax is also defeated, Tetrax returns Ben and Gwen to Earth and departs.
