This game shows how one natural move can turn a good game into a lost position.
1.e4 c5 2.Nf3 d6 3.Nc3 Nf6 4.g3 g6 5.Bg2 Bg7 6.0-0 Nc6 7.d3 Bg4 8.h3 Bd7 9.a4 0-0 10.Ne2 a6 11.c3 b5 12.axb5 axb5 13.Be3 Qc8 14.Rxa8 Qxa8 15.e5 Nd5 16.exd6 Nxe3 17.fxe3 exd6 18.Nf4 Qa2 19.Rf2 Ra8 Here the position is roughly equal. [19...b4!? 20.Ng5 Ne7 is an alternative not pinning the rook on the diagonal]
20.Ng5 Looks primative but it does have a point.
20...h6?? A blunder missing whites next move which wins the queen or mates black in two moves. [20...Qa1 is about level after an exchange of queens. 21.Qxa1 Rxa1+ 22.Kh2 Ne5 (22...Nd8 23.Ne4 Ra6 24.Nd5 Be6 25.Nef6+ Bxf6 26.Nxf6+ Kg7 ) 23.Ne4 Re1 ]
21.Bd5 Qa1 22.Bxf7+ White mates next move with Nxg6. 1-0