I'm just trying to make sure I'm playing this character correctly. Knifehead's special power reads "Bone Knife Headblade Slash and Slice: Give Knifehead a move action; its speed and damage values are locked for this action. Move Knifehead along a direct path and after actions resolve, make a close combat attack as a free action that targets all opposing characters that were moved through. Each hit character is dealt damage equal to Knifehead's damage value." So basically he gets to move X numbers of squares, and he automatically breaks away from opposing characters until he finishes his move, correct?

Well, he automatically breaks away normally, because he's a colossal. Nothing in this power changes that. But he could still be stopped by someone with Plasticity, though.

Ah, that makes sense.

Nope.

Giant Reach: This Character ignores characters' Plasticity. . .

Good catch. I forget about the trait giving them giant reach.

So Knifehead moves through characters squares as if he's using improved movement ignores characters?