Albert Wesker (Character)

Albert Wesker is one of the central characters in the Resident Evil franchise by Capcom (or Biohazard in Japan). He was introduced in the original game and was the captain of U.S. police team STARS. Initially introduced as a supporting character in the first game, he has been one of the primary antagonists throughout the series, where he usually manipulates story events behind-the-scenes.

He was a man who sought to replace the entire race through mass extinction and forced evolution, these thoughts causing Wesker to become very power-hungry. To this end, he was affiliated with the Umbrella Corporation as one of its most promising researchers, and at the same time participated in illicit activities by going undercover as S.T.A.R.S. captain in Raccoon City. After everyone found out about his betrayal, Wesker fakes his death and gains superhuman powers from an experimental variant of the Progenitor virus. He then starts working with Umbrella's mysterious rival company, TRICELL, until his defeat in Resident Evil 5.

Chris Redfield was the one who found out that Wesker worked for Umbrella, killing his plans. That's why he started to hate Chris, wanting nothing more than to destroy the guy.
In terms of personality, Wesker was a cunning, deceptive, and highly intelligent bio-terrorist, usually preferring to observe the action from behind the scenes and then strike when the opportunity presented itself.