user-1: In the King's gambit, a strong opponent has played against me(as black):
1.e4 e5 2.f4 exf4 3.Bc4 h6(trying to hold onto the f-pawn).
I have found a variation where White probably has a strong initiative, but he still insists that Black is fine and is slightly better.
4.d4 g5 5.h4 Bg7 5.hxg5 hxg5 6.Rxh8 Bxh8 7.Qh5
I have stopped my analysis here, since Black has a refutation 7... Qf6. I put this position into the engine, which gives White a large advantage, but Black has an extra pawn. Where did I go wrong?

user12873: So I'm not sure if you're asking where you went wrong analyzing this line for Black (because of the large advantage the engine gives to White) or for White (because you think Black being up a pawn is important).
If you mean analyzing for Black, 4...g5 is a poor move (3...h6 is also not great, although Black still seems alright). There are a few better moves, such as 4...d5. The point is to meet 5.Bxd5 with 5...Nf6, and 5.exd5 with 5...Bd6. Probably a more challenging try for White would have been 4.Nc3, aiming to prevent ...d5. Coming back to Black's point of view, by the time 6.hxg5 is played White already has a clear edge. But still a better response would have been 6...Nc6 or 6...d5; 6...hxg5 gives White a winning position.
If you mean analyzing for White, the only arguable improvement in your analysis is 4.Nc3 instead of 4.d4. By the final position after 8...Qf6, the engine gives White a huge advantage - the lost pawn is irrelevant. White could follow up with Nc3, Nf3, e5, etc, enjoying an overwhelming initiative. Reaching this position is a disaster for Black, and definitely not for White.

-1: <p>In the King's gambit, a strong opponent has played against me(as black):
1.e4 e5 2.f4 exf4 3.Bc4 h6(trying to hold onto the f-pawn).
I have found a variation where White probably has a strong initiative, but he still insists that Black is fine and is slightly better.
4.d4 g5 5.h4 Bg7 5.hxg5 hxg5 6.Rxh8 Bxh8 7.Qh5</p>
<p>I have stopped my analysis here, since Black has a refutation 7... Qf6. I put this position into the engine, which gives White a large advantage, but Black has an extra pawn. Where did I go wrong?</p>
 12873: <p>So I'm not sure if you're asking where you went wrong analyzing this line for Black (because of the large advantage the engine gives to White) or for White (because you think Black being up a pawn is important).</p>
<p>If you mean analyzing for Black, 4...g5 is a poor move (3...h6 is also not great, although Black still seems alright). There are a few better moves, such as 4...d5. The point is to meet 5.Bxd5 with 5...Nf6, and 5.exd5 with 5...Bd6. Probably a more challenging try for White would have been 4.Nc3, aiming to prevent ...d5. Coming back to Black's point of view, by the time 6.hxg5 is played White already has a clear edge. But still a better response would have been 6...Nc6 or 6...d5; 6...hxg5 gives White a winning position.</p>
<p>If you mean analyzing for White, the only arguable improvement in your analysis is 4.Nc3 instead of 4.d4. By the final position after 8...Qf6, the engine gives White a huge advantage - the lost pawn is irrelevant. White could follow up with Nc3, Nf3, e5, etc, enjoying an overwhelming initiative. Reaching this position is a disaster for Black, and definitely not for White.</p>
