Who Would Win In A 1v1

Sion

Sion's been mentioned by a rioter (reav3 I think) that Sion charging could knock down Galio, who's like 300 tons or something ridiculous.

The Mountain is just a resurrected guy who may or may not have a head. That's like asking "Who would win Lord Marshal Sir William of Pembroke or the Hulk?" Lord Marshal may be awesome, a far more interesting person and the greatest knight who ever lived. But he ain't gonna do squat to the Hulk.

Sion would eat him in breakfast.

Sion would win easily. Keep in mind that Sion is considered to be Galios equal and that Galio is a gigantic golem who can easily trample entire houses.