He was voiced by Charlie Warren.
Mr. Tenpenny is a businessman at his core, and most of his evil deeds are motivated by profit and a desire to satisfy his client base. He wishes to obliterate Megaton for the simple cause of he and his clients considering it unattractive and view obstructing.
Mr. Tenpenny is also a prominent ghoul biggot, meaning he considers ghouls unsavory and less than human on the sole premise of their appearence. While he does hold biggoted views himself, he is not averse extending his services to a ghoul clientelle, as long as it does not interfere with his already established customer base. Because of this, the Lone Wanderer has the option to convince Tenpenny to take the local ghoul population lead by Roy Phillips as clients, after weeding out the tower's most stubborn biggots.
Allistair's biggoted views and elitest attitudes have earned him many enemies, particularly among ghouls. One ghoul named Mr. Crowley may even commission the Lone Wanderer to assassinate Mr. Tenpenny, though their are also alterior motives involved in that assignment. Also, even if the Wanderer peacefully resolves the conflict between Roy Philip's group of ghouls and the residents of Tenpenny Tower, Philips' ghouls will eventually kill Tenpenny and all other non-ghouls living in the tower, and it is never truly revealed who is responsible for the events that lead to this revolt.
Though Allistair is a cold and ruthless businessman, and an arrogant snob, it is worth noting that he can be reasoned with, and Fallout 3 may actually be played entirely non-evil with good choices yet maintaining a good relationship with Tenpenny. This causes his level of villainy to be dependent on player choices.
Fallout: New Vegas