wwall: Probably a lot of missed opportunities in this endgame. Instead of 50.Kb6, perhaps best is 50...Ka6, avoiding the check after ...Rb5, or 50...Re6 and 51...Rexc6 should win easily.
After 51...Rf5, White still has 52.Re6 and 53.Rexc6.
After 52...Bf7, perhaps best is 53.Rc1, and if 53...Be8, then 54.Rc8 Kf7 55.Kc7.
After 53.Ka7, perhaps best is 53...Be8 and hope to repeat the position 3 times for a draw.
After 53.Ka7 Rf4 54.Ka6, 54...g5? looks like a losing move. Perhaps best for Black is 54...Bb3, and if 55.Rxc6, then 55...Rxb4 may be drawish.
Instead of 56.Ka5, perhaps best for White is 56.Re5, threatening 57.Rxg5. Black can't play 56...Rxb4 because of 57.Rf5! which wins for White.
Instead of 57...Rf2?, perhaps best is 57...Bd5, holding the c6 pawn.
After 57...Rf2 (threatening 58...Ra2 mate), instead of 58.Ka5, best seems 58.Rc8+ (not 58.Rxc8 Be8) 58...Kg7 (now Black does not have ...Be8 pinning rook and king) 59.Rxc6.
After 59...Rf2 again, White now plays 60.Rxc6 instead of the stronger 60.Rc8+ first. The game should have drawn at this point.
After 63.Kb5 Black played the losing move 63...Rb2+??. The drawing moves are 63...Rc3 or 63...g4 or 63...Kf7.
After 63...Rb2+?? White wins with 64.Ka6, but 64.Kc5 is a shorter win for White after 64...Rc2+ 65.Kd6 Rd2+ 66.Ke6 Rc2 67.Kd7 Rd2+ 68.Kc8 and 69.c7, 70.Re5. Black could have dragged the game out a lot longer after 64.Ka6 Rc2 65.Kb7 Kf7