[@Zero Hex]

Perhaps it could take some degree of extra mental effort to impart a force to someone who isn't willing to be moved, rather than specifically channellers? That'd totally bypass the issue of moving inanimate objects while still preventing someone who's only 80-90lbs. from being extremely easily flung like a shot-put. We're mostly looking at a minmaxed character at the moment - not very easy to put forth a 100% satisfactory solution that everybody can accept fresh out of the box if a character's powerset is a hard counter specifically to 'big hits', and more specifically, big melee hits.

Look at any boxer out there. They can typically block most punches without breaking a sweat, but in any reasonable matchup, punches will eventually get past their defenses simply by merit of their defense not protecting the one specific spot that a shot leaked through at that moment. Likewise with swordsmen and other weapon users. Nullification is extremely useful, but only impenetrable in specific circumstances - extremely one-sided fights, narrow corridor fighting, etc. We're talking about a huge guy with muscles for brains here - any number of things can completely bypass his tricks. I don't really consider it to be a big issue if he can stop, say, a greatsword, so long as the guy with the greatsword is perfectly capable of letting go of the weapon and quickly punching him in the face instead.

[@tipssyCalibrator]

I'll write in roughly a half second of preparation time for focusing his momentum modification tricks. Add in quarter-second reaction time, bringing it up to effectively 3/4ths of a second to block a strike. That should be sufficient to allow for extreme defense against massive strikes, but still long enough for the characters focused on rapid strikes to cause mayhem. Sound good?