Sylvester Stadler
In-game
Stadler can only appear if the player goes down Reinhard Heydrich's path for Germany and chooses the Waffen-SS branch of his focus tree during the civil war. While Stadler leans towards Heydrich more than Himmler, unlike the other two leaders (Herbert Otto Gille and Paul Hausser), he does not wish to continue the fight, seeking to ensure his land is in the right hands, and instead prefers to leave Germany and retire in Hungary - a position many of his men, also weary of fighting, share.
Trivia
In real life, Stadler was notable for ordering a court martial of one of his subordinates Adolf Diekmann for the latter's role in the Oradour-sur-Glane massacre, an event which shocked many who heard about it on both sides of the war, notably Erwin Rommel. The commune the event took place in (Oradour-sur-Glane) was not rebuilt as a memorial. It's likely that his role in Heydrich's Germany was influenced by his relation to this event.