damn this iz hard

Keep on hitting him in the back, when he drops the allspark quickly pick it up and hit him with it. ( don't throw it, it doesn't work. Then optimus and megatron will battle one on one. You just keep running around him shooting. He will eventually die but if your low on health, kill a drone on the sidelines ( there are only four(4) so be careful).

To beat Megatron use a transformer with high agility, such as the maxed out agility Raider at level 20. He is as nimble as a ship so just keep going behind him and hitting him in the back. When he drops the Allspark pick it up with X and hit him using A. Your charcter will die but will make Megatron non-invincible and Optimus will take up the fight. MEgatron is incredubly strong, so to avoid him completely jump onto the very low southwest building, stand on the edge and use heavy weapons. Occasionally Megatron will use his heavy weapons and knock you back, but just get back on the edge and shoot him some more. Otherwise, just stop him from using his blasters, as they can either knock you onto the floor and leave you vulnerable, or take away a huge chunk of your health. Knock seven bells out of him with melee attacks (A) to prevent him using blasters. Good luck.