How do you beat end game misson on transformers autobots

To defeat megatron I suggest you start the mission with a fast vehicle. When you get one, start. What you have to do is sneak up inback of him, and hit him. (press A) You will have to hit him about 4 or 5 times. When you see him drop the allspark, pick it up and get in front of him.Then, hit him with the A botton. Now you be Optomus Prime and shoot him to death. I suggest you get a-lot of extra healthes.