Alright, serious response time.
Your officer messing with a war by giving one side absolute power is the most severe violation of the Federation's laws and principles. Yes, the Prime Directive can be violated at times based on extenuating circumstances, but your scenario is very black and white. I can't imagine a worse crime that could be committed by a StarFleet officer outside of treason. I would expect being kicked out of StarFleet at the very minimum and life in prison as the most likely outcome.