patzer2: White's 20. Qxc4?! indicates he was too anxious to jump into an inferior endgame with his super GM opponent. Better was 20.Qd3!, when play might have continued Qc7 21.Rab1 Rc8 22.a3 Qb6 23.Nd2 Rd4 24.Qf3 Qc7 25.Ne2 Ra4 26.Nc3 Rd4 27.Ne2 Ra4 28.Nc3 Rd4=, with a draw by threefold repetition. White missed several chances to improve his endgame play:
Instead of 26.Rd1?!, White could have played 26.Rb1!, when play might have continued 26...b5 27.Rb3 h5 28.Kf1 g4 29.hxg4 hxg4 30.Nh2 g3 31.fxg3 fxg3 32.Nf3 = with equality.
Instead of 28.Nd4?!, White should have considered 28.Ne1 b5 29.Rd3 Rc4 30.c3 Re4 31.Kf1 Rxe5 32.Rd8+ Kg7 33.Nd3 Be7 34.Rd7 Rd5 35.Rxe7+ Kf6 36.Nxf4 gxf4 37.Ra7 Rd6 38.Ke2 e5 39.g3 fxg3 40.fxg3
with survival chances.
Instead of 30.Rd8+?, which loses immediately, White could have put up more resistance with 30.a4 Rc5 31.Rd7 Rxe5 32.Rxb7
.
Black still had a win after 34... a5?!, but could have expedited the ending with 34...Kxe5 35.Rh5 Kf6 36.Rh6+ Kf5–+.