Samuel Hayden

General Hayden is the commandant of the UAC space marine garrison in the Doom 3 novels. In the Reboot, he is now known as a robot known Samuel Hayden, who is the Scientific Director of Mars.

Doom 3 Novels
Hayden is opposed to Swann and Campbell's investigation of the Mars facility, warning them that Betruger won't let them pull the plug on his operation.

Doom 2016
He appears in the reboot and tries to persuade the protagonist, Doomguy, to assist him. He is harshly rebuffed twice at the beginning of the game, though Hayden claims to be willing to accept full responsibility for Hell's invasion. Hayden appears at first glance and throughout the campaign as a minor ally (and Human until his appearence) until his betrayal at the end of the game, taking the artifact so he can rebuild UAC on Earth, and seals the Doom Marine back in his tomb.

Trivia
He was slated to appear as a secondary antagonist in Doom 3, but was cut from the game, making Betruger the main antagonist.