This is easiest against a boosting partner online. Let them capture most of your pawns and then paint themselves into a corner and lose. It can be earned against the AI, but this is a hard one to use a simulator online for since those often focus on winning via attrition. If you try this with normal game play, I would suggest focus on getting the enemy king pinned in a corner and then deliberately sacrifice pieces until you have 2 fewer than he does. At that point, checkmate the king and the achievement will unlock.