Based on the synopsis, and a few other things, I'm going with Garth of Izar. In TOS lore, he was a Fleet Captain and one of Kirk's personal heroes. I can imagine a plot in which he essentially goes rogue and convinces a significant chunk of Starfleet to go with him. Maybe he's insane as he was in the old TOS episode, or maybe he's just disaffected or pissed off about something. Either way, he evidently brings the hammer down on Earth in some way--though I'm not convinced the "detonated" part is to be taken literally--before taking off for this "war zone world" where he presumably intends to cause further trouble.
As for being a one-man weapon of mass destruction, Garth did have special powers taught to him by the Antosians, though they were limited to shape-changing abilities. No reason they can't expand on that, though, to make him more generally superhuman, able to shrug off Vulcan nerve pinches, etc.