Candidates
Bxh6
Nf5
Ng6
Bxf7+

After trying several lines using the above candidates I came up with the following

18 Ng6 the idea now is to chase the to the c6 square if 18...Qf6 19. Bg5 Qd6 20. Rad1 Qc6 21. Bxf7+ Kxf7 22. Nxe5+

Black loses the - now to look

18.Bxh6 gxh6
19.Qg6+ Bg7
20.Nf5 Qf6 (the only other move is Qf8...black has to protect against mate on the g7 square. both moves lead to the same fork) 21.Bxf7 Qxf7
22.Nxh6+ wins the black queen

the only way out for black is instead 21.Qxf7, go with 21.Kh8. After a series of forced exchanges black is way down in material.

21 ...Kh8
22.Bxe8 Qxg6
23.Bxg6

Black is way down in material. The position isnt hopeless but white is winning.

- 18 Bxh6
- 18 Nf5
- 18 Bg5
- 18 Ng6
- 18 Qg6

There are others, but they don't seem as forcing. A big concern of mine is the bishop on b3. This piece seems to be key in hold black's f-pawn in place. Should black have a chance to play ...Nxb3, our attack would likely wither. So our moves must be at least a little "forcing" to stop that move.

Note also that the black queen must keep an eye on f7 to stop Bxf7+ picking up an exchange or Qxf7+ leading to mate in many variations.

The more I look at it, the more I like

18 Bg5

This attacks the black queen (forcing) and is immune to capture by the queen (18...Qxg5 19 Qxf7+ Kh7 20 Qg8#) because it abandons protection of f7. It also cannot be taken by the h-pawn (18...hxg5 19 Ng6 and 20 Qh8#). What's black's response? He must maintain protection of f7 so

18...Qd7

Time to bring in fresh troops! How about

19 Rad1

Threatening the queen (who cannot move as this will abandon f7). That means

19...Bd6

So far our moves have been forcing enough. Let's try to keep the pressure on with

20 Bxh6

I hope this is right. It's not nearly as forcing as our previous moves, but it does have threats. Black has a couple of replies:

- 20...gxh6
- 20...Nxb3

First, let's consider the capture. After

20...gxh6

white can play

21 Qg6+ Kh8 22 Qxh6+ Kg8 23 Qg6+ Kh8 24 Bxf7

threatening mate with 25 Qh6#. The only way I see to stop this is 24...Bf8 or 24...Qxf7, but these both give up the queen (we took the pawn with check on move 22 rather than the bishop capture in case black does want to go for this line, we have an extra pawn) and white should win easily.

So I think the second line is key, let's look at

20...Nxb2

white ignores the capture and responds

21 Bxg7!

threatening 22 Qh8#. If

21...Kxg7 22 Nf5+ Kf6 (22...Kf8 or 22...Kg8 allow a queen check on g5 or h6 and mate next move) 23 Qg4+ Ke6 (23...Kg6 24 Qh6#) 24 Ng7#.