1: Aizen, Immortal god like Shinigami that controls your very grasp on the world through your 5 senses.
2: Madara, either an immortal God with so many ways to kill it would be easier to note ways he can't kill you.
i) Killed by Kitten Summon.
ii) Killed by sharpened pencil.
iii) Killed by eraser.
iv) Killed by Wood Clone & Bodily dismemberment... Thanks Tsuande.
Ooooor an unstoppable Shinobi with the same pool of jutsu but limited (Understatement of the century) chakra.
3. Whitebeard. Able to break apart space itself with his fists and signature staff-thing. I don't actually know much about him, but pitting him against the other two would be suicide.