Mine would be......
Jygylagg The Daedric Prince of Order.
And judging from the TESO Cinematic Trailers Molag Bal The Daedric Prince of Schemes and Deceit is a friggin’ badass too.
Alduin is supposed to be immensely powerful since he is the first aspect of Akatosh.
Akatosh is probably the most powerful deity. Judging from the Lore