War criminal

A war criminal is someone who is accused of committing a war crime.

In an alternate reality, Nero was considered a war criminal, after he destroyed the planet Vulcan and caused the deaths of six billion people. 

Gul Darhe'el was considered by many to be a war criminal. 

Worf and Ezri Dax were to be charged executed by the Cardassians for being war criminals after being taken prisoner by the Breen in late 2375. 

Dukat was accused of being a war criminal for his actions during the Occupation of Bajor. Kai Winn Adami once told him that she didn't forgive war criminals.