Who had the best honorific?
Alexander the Great*
Charles Martel (meaning "the Hammer")
Richard the Lion-Hearted
Mehmet the Conquerer**
Sulieman the Magnificent
Ivan the Terrible

The clear all-time winner is William the Conquerer, not for that title, but for his original honorific: William the Bastard

*also Peter the Great, Catherine the Great, Frederick the Great; so, hardly unique
**also William the Conquerer