Complex sentence: He was trained in unarmed combat under the guidance of Emma Frost and was extensively trained in the use of the staff by his long-time teammate Shatterstar-who he eventually matched in a record time of only a dozen tries.
Split into simpler sentences: He was trained in unarmed combat under the guidance of Emma Frost. He gained extensive training in the use of the staff by his long-time teammate Shatterstar, whom he eventually matched in a record time of only a dozen tries.