the combination of Air Slash and Serene Grace allows Togekiss to fence off many foes, posing a decent offensive presence. With Air Slash's increased 60% flinch rate paired with paralysis, the opposing Pokemon is left with just a 30% chance of successfully moving.
So first off, 30% without counting King's Rock. However;
>All moves that actively deal damage and do not already have a chance to flinch will gain a 10% chance of flinching the opponent. (This chance doubles to 20% if the holder has Serene Grace.)
.: King's Rock is basically useless.
30% Chance of moving.