Dr. Victor Presper was going to be the main antagonist in the cancelled version of Fallout 3, Van Buren. He is a brilliant mad scientist who used to work for the NCR and has the goal of preserving the "master race" of pure humans, as opposed to mutants. To this end, Presper intends to use an orbital satellite called the B.O.M.B. -001 to launch nuclear weapons at parts of the Earth, as well as a virus engineered by a computer called the ULYSSES (not to be confused with the canon character). He would keep the humans that he had chosen to save inside the Boulder Dome until he deemed it safe for them to go out into the even more devastated than before world and start repopulating it, and it would have been up to the player to stop him, had the game ever been finished.
Fallout: New Vegas
Van Buren (Cancelled)