Fabian Cortez is a mutant who can cause a superpower to increase in magnitude to the point of destroying the owner.
He is the leader of the Acolytes and used to be a loyal follower of Magneto, but actually wanted Magneto out of the picture so he could lead the Acolytes himself.
Cortez was killed on the mutant island Genosha during bombings, but was resurrected by Selene and fought the X-Men and Deadpool on Utopia.
Cortez and Deadpool fought in the following comics:
X-Force Annual #1 (2010)