Transformers: Autobots and Decepticons/Decepticons

How to beat Jazz As Megatron
Well, Megatron has maxed firepower so you should use and abuse it! Tap Y to get a lock on and use the non-blaster weapon (you could use the blaster but the purple bolts he fires looks much better. Jazz is ultra-fast so you should strafe...a lot. The most annoying thing that isn't him and his ultra-fast speed is the blue bolts he shoots. While you are still using the combat shooting form, strafe back. They splash so move a bit further. Change the camera view once in a while in case you lose sight of him. He can’t melee you but he makes Megatron bleed bit by bit. Another thing, as you probably know, the turrets you has to destroy fires anti-air missiles and guess what, so can Jazz. Of course, it's anti-air, he only fires them while you are in the air. He usually strafes to your left or jumps over you. I don't suggest melee, as Megatron is the slowest character...ever. That covers everything, but if you want to use the blaster because it's accurate to shoot fast things like Jazz, sure, go knock yourself out! (It means "Go for it!")

How to beat Starscream as your custom character
To begin with, Starscream has the Allspark, he's invincible. Your objective isn't to kill him at all. It's to get the Allspark out of him. How? Hit him with 5 melee attacks. Basically make sure you have the Hot Rodder, Raider or very fast car equipped, then when Stascream stops (After an attack) jump and run behind him and hit him with a melee attack (A button). After hitting him 5 times, he will drop the Allspark. Pick it up (X button) and hit Starscream with a melee whilst holding the Allspark.

How to beat Starscream as Megatron
After owning Starscream with the Allspark as your custom character, Megatron takes over. Basically go into your Cybertornion Jet form and chase Starscream around the map, shoot at him as much as possible. Eventually Starscream will land, avoid the Missiles he'll fire and land as well. Then shoot at him whilst strafing to avoid his attacks. Eventually he'll fly off and you'll have to repeat the process. If you need health, go kill the Choppers or destroy the lamp posts & trees whilst Starscream is on the building. The instant you have full health or Starscream goes back to his F22-Raptor form, go into the Cybertronion Jet form and follow him. If he gets to far ahead you lose automatically. Eventually you'll be able to finish him off. Also beware the choppers that fly about and shoot you, they are a pain especially when you are getting battered by Starscream. Once you beat him, congratulations! You've beaten the game's Story Mode!