This achievement has to be unlocked versus the AI and cannot be earned in MP. Start a classic game against an AI of difficulty 0. Capture the majority of their pieces and then checkmate the king. Your final move is what counts for this achievement. The piece that places the enemy king into checkmate needs to be varied such that you win one game with each piece as the finisher. Your king cannot place the enemy into check, so it is the remaining five types (pawn, knight, bishop, rook, and queen) that must be used. As such, it takes a minimum of five games to earn this achievement.