Galvatron

Whether he's born from the fires of Unicron himself, an ancient Transformer warlord, or something else altogether, one thing is always certain: Galvatron is a focal point of power and madness given form. He is blind to all but his lust for power; his whims and desires can be sacrificed in a moment's rage. Not even his own subordinates are safe. Though he is not beyond the capacity for long-term goals it is his unpredictability and casual disregard for any and all life that strike such horror in friend and foe alike. Truly, the Decepticon leader is without any sense of empathy.

In most universes, Galvatron was once Megatron but was reborn from his death throes in a Faustian pact with Unicron. He retains the memories and spark of Megatron but his personality was significantly altered after the near-death experience, massive physical upgrade and reprogramming; just ask Starscream about the difference. And that was before he went insane. The cause and extent of Galvatron's madness varies between different timelines, as does his physical power. Sometimes he's all but invincible.