William, the duke of Normandy: 1048 to 1060

Attacking Brittany for any reason, is only going to embroil you in an untimely war that expands to include Anjou, Maine, and God alone knows how many other powers. When your cousin king Edward dies in the not-too-distant future, you are so entangled and committed to the war you have started, that you cannot break free to prosecute your claim to the throne. History only knows you as William the (bloody) Bastard.

William the bloody bastard