SCOTT PILGRIM VS THE WORLD THE GAME

To get this achievement Knives must be at least level 11 to unlock the head stomp ability. To get this achievement easily go to the level subspace highway at the bottom right part of the map. Go through the first part normally grab the sword of love on the cloud and do Gideon's 1st phase normally. After you're done with his first phase when he gets near you want to start head stomping his arms or heart. To do the head stomp ability jump up in the air and hit Y and once you bounce off the enemy keep hitting Y while you're in the air to do the move again and again on either Gideons arms while he is covering his heart or you can do it after he smashes the ground and reveals his heart. This may take some tries to do it since Gideon sometimes likes to get into a pattern of just punching you again and again once you get up. Here's a video from a guide for the 360 version that still works (Video has been time-stamped to show just this achievement) Note: All of your head stomps cannot be interrupted and all head stomps must do damage or else it won't count if you just hit them while they're guarding or in an immune phase.

I've noticed people having trouble with the other guide so here's a tip.

Phase 2 Gideon will ALWAYS back up after 8 consecutive head stomps while his arms are covering his heart. To get the achievement, wait until he shows his heart, then stand above him, double jump, and start your head stomps from there. If you time it right, you should be high enough to dodge his skull attacks and not break your combo. Alternatively, you can stay below him when you start your combo, as shown in the video linked below. Credit to Gaming with Abyss for the video and Gamechamp3000's Scott Pilgrim video for the tip about Gideon backing up after 8 hits.