Derek Clifford Simmons is the primary antagonist of Leon Kennedy's campaign in Resident Evil 6.
Simmons is the National Security Advisor and a close friend to Adam Benford. He is the leader of a secret organization known as "The Family" whose ancestor founded, using its vast political influence to maintain world order. He hired Ada Wong to acquire the G-Virus while overseeing the missile strike on Raccoon City, taking her resignation hard as became Sherry Birkin's legal guardian. He secretly used a sample of her G-Virus-enhanced blood to synthesize the C-Virus, using a variant of it to turn his top scientist Carla Radames into a clone of Ada Wong he later deploys to capture Jake Muller. Simmons then orchestrates the assassination of president Benford in fear that his act of declassifying the Raccoon City incident would jeopardize national security, coercing Helena into infecting the president with the C-virus while causing a viral outbreak in Tall Oaks to cover his tracks with Helena and Leon as his scapegoats. But Simmons was undone by a revenge-driven Carla Radames using the C-Virus, forcing him to travel to China where he gets infected with an Enhanced version of the C-virus and is forsaken by the Family. This results in Simmons being able to mutate into a variety of monstrous forms that include a giant insect-like form from absorbing C-Virus infected zombies, before he was ultimately killed.