X-Men Legends II: Rise of Apocalypse Hints

Complete the first two acts. At an X-Traction Point in Act 3,
they will be available. On the change character screen, press
L2 to switch between available skins.

Before you go battle, set all players to aggressive and get 4 X-treme squares, and make yourself as juggernaut with PATH OF DESTRUCTION as your R2-Triangle attack, when your there ignore stryfe completly (your partners will attack him) and attack the brain trust with PATH OF DESTRUCTION, when all of them are destroyed, attack stryfe with your teammates

P.S. If Stryfe comes near you, beckon your teammates

When you are defeating him at the end it is hard for him to go up the stairs with tubing so use a ranged attake to kill him.