Osmund Saddler is the main antagonist of Resident Evil 4.
Saddler is the leader of Los Illuminados, the cult responsible for Ashley Graham's kidnapping. Saddler plans on infecting Graham with a sample of Las Plagas, in hope that she will return home and infect higher-ranking members of the U.S. government. Saddler then attempts to control them and seize control of the country, and then the world.
He uses samples of Las Plagas to infect and control villagers and even a local castellan Ramon Salazar to perform his bidding. However, his plans are foiled by the combined efforts of Leon Kennedy, Ada Wong and Luis Sera. Kennedy, with the assistance of Wong, kills Saddler near the game's conclusion, and destroys his research and production complex.