Outsiders still call him The Arm.
Coach's mutant abilities were all based in his arm that was removed in a mission. The arm was larger in size than normal and displayed super-strength and was thought to have other powers as well. Coach was recruited to train and mentor the X-Force, but actually behind the scenes plotted which members would die, and actually attempted to kill the Orphan and U-Go-Girl on his own. When he attempted to kill the two mutants, he was shot and killed himself by U-Go-Girl.
Coach was created by Peter Milligan and Mike Allred in 2001 and first appeared in X-Force # 116.