History
When Mr. Sinister succeeded in corrupting the Quiet Council of Krakoa, turning them and in time every Krakoan mutants into modified clones of himself, one of their first actions was offering artificial X-Genes to humanity in order to welcome them into the Resurrection Protocols.
After lobotomizing Krakoa with an orbital laser, the Sinisters blamed Orchis for the attack. With the Resurrection Protocols thrown into disarray, Captain America led the Avengers in joining the X-Men and other superheroes for an attack on Orchis.
With Orchis destroyed, Cap was convinced to accept X-Gene treatment as a way of showing solidarity, unaware that this meant that he too would become a Sinister-clone. Under Sinister's control, Cap and the other human primaries on the Avengers pushed the team into increasingly extreme, antisocial and malevolent actions.
This climaxed in a war during which Cap seized control of the United States Government after murdering the sitting president. Cap and the Avengers were killed and defeated by the X-Men as a way of propping up Sinister's grip on the planet.[1]