Shockwave

Transformers Prime Beast Hunters S03 E03 Prey 108

Coldly logical and lacking in personal ambition or ego, Shockwave was at first the least of Megatron's concerns. Shockwave's sheer destructive power was tempered only by his dispassionate approach. No blood lust, no battle rage...just the most effective and economic approach to any given scenario.

Unfortunately for Megatron, Shockwave concluded that his leader's all-consuming passion for conquest was not the optimum solution...therefore, Megatron should be removed, and Shockwave himself should lead the Decepticons. No malice, no ego, just simple logic.

It's actually revealed in the past that Shockwave wasn't evil. He was once a good senator that the Autobot Senate had kidnapped subjecting him to being reprogrammed into a cold and emotionless machine. Worse than that, they destroyed his face turning him into the one-eyed Decepticon he is now to make him feel less human looking and more machine like.

Now Shockwave not only wants Cybertron for the Decepticons, but also desires payback on the Autobots for what he believes applies the same to them: being cruel like the senate had done to him. It was Sentinel Prime himself who gave the order through the Autobot senate to stage an accident to Senator Shockwave's headquarters and make him less recognizable through a hideous appearance his emotions hampered by the Shadowplay program he had his men implanted into him.