User blog comment:HozzieHozzbourne/Strongest champion outside of the game/@comment-6271162-20130920190414

Syndra. She is able to conjure anything. Thats what I call real power. We know that the League limits the powers of the fighters so somebody like Brand can't just obliterate everything, so imagine Syndra outside of the League. She lifted an entire stronghold (!) to the air and let it hang here indefinitely (!!) when she was but a child (!!!).

Lissandra could be another possibility because of her overwhelming knowledge she must have achieved over the millenia and due to her sheer amount of power.

Brand is also extremely powerful, marked by his own words, he is the fire that cleanses the world.

Xerath is almost a god, transcending the limits of a mortal effectively becoming the avatar of magic itself.

Last one is Zilean, of course, because, you know, he can time travel...