Autobot, friend of Optimus Prime, his old master, who turned his back on him to help the decepticons rebuild their planet back, the Cybertron.
Sentinel Prime : I'm sorry I betrayed you, Optimus.
Optimus Prime : You didn't betray me, you betrayed yourself, *Points gun at Sentinels Head*
Sentinel Prime : No Optimus, NO!
Optimus Prime : *Bang bang bang*