Samuel Hayden

Samuel Hayden is the Chairman of the UAC who oversaw the Argent Energy research projects at the UAC Mars Base. He serves as the true main antagonist of Doom (2016) and presumably the main antagonist of the upcoming Doom Eternal.

History
Samuel Hayden was born to the powerful Hayden family and was a very prodigious intellectual and philanthropist. After he was appointed as General Director of the Global Science Council, the UAC recruited him. Soon after Argent plasma was discovered on Mars, Hayden subsequently took over the leadership of the UAC.

After the Argent Energy Tower was constructed in 2127, Hayden was diagnosed with an incurable brain cancer and left with a few months to live. Hayden avoided his death by transferring parts of his brain into a 3-meter tall mechanical body. It was implied that Hayden chose this form for his expeditions into Hell.

Hayden led the first manned expedition into Hell in 2145 in which he discovered the Doom Slayer, simply called "Doom Slayer". He had the Marine recovered and kept him personally under his watch away from the auspices of his disgruntled colleague Olivia Pierce. Hayden's relationship with Pierce gradually deteriorated due to her deranged, religious obsession with Hell which ultimately corrupted her.

After Pierce betrayed Hayden and planned to open the gates of Hell, Hayden awakened the Doom Marine and tried to persuade him to assist him in stopping Pierce. 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.

After the Doom Marine killed Pierce and stopped Hell's invasion, Hayden betrays the Doom Marine, taking the "Crucible" artifact from him to continue exploiting Hell's resources for the sake of humanity's progress before sending the Doom Marine to an unspecified location. Before he does so however, Hayden states his certainty that he and the Doom Marine would meet again.