The safest way to get this is to set the game to easy and load up 'Training Time'. Use Four Arms when you are going against enemies. Be careful when your jumping between gaps and don't stand to close to edges while fighting enemies. If you run out of energy or get knocked out of alien form, run around the area until your energy recharges. If you get a chance to upgrade an alien form, upgrade Four Arms to get stronger and better combos. At the end of the level you will have to fight the Queen Ant, which isn't hard at all. Just avoid any fights while you are controlling Ben and always attack as Four Arms. If you die and restart from checkpoint, you will have to start the level again.