Spoiler :Is it Bxg8?
It looks nasty for black.
Why yes it is. It's not only nasty, it's immediately decisive. Black might as well take the free bishop with Bxe3+ but after Kh1 there are no good options. Qf7+ (and fxg6 first in some lines) are just decisive. Best line for black is; Kg7, Qf7+, Kh6, f6 and the rook will be lost not to mention the unfun position of the black king and total lack of counterplay. At around +6.00 black might as well resign and that's if he found this, the best line.

)

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Not if I can get to the 
) I am often appalled at what I missed.

by accident. I managed to hold on pretty well for 18 moves though until I made another error on g5 actually with Bxg5. In retrospect the real ender for me was 19. ... h6, I should have played Kf6. I subsiquently made a few more blunders & the game was over.

