Toughest defeat of my life

Simply put, I have lost alot of games in my life but this was one of the only games I almost punched the wall right afterwards. I would have been nice to beat a "titled" player and a "world champion" (U10 WC is a decent accomplishment imo). Alas it was not meant to be. 

It would be nice if you guys could help give me some pointers in this game. It was a tournament i played about 5months ago and was my second in the last 3-4 years. The last 2 tournaments i have played I have played massively above my existing rating thanks to Chess.com.

Isn't 26 gf+ good?

That was definitely a tough loss.  I felt like slugging the wall for you too. 

Yes i think it is better. The line i looked at was

Which left me in a better posiion and up a pawn which is a long hard game for me to win. I wanted to win quickly and forcefully.

Yeah, that's what I was looking at too.

I'm looking at moves 17-21. What about lining your rooks up on the h-file before taking the g-pawn? Might that have provided the line you were looking for? I am thinking about lining those rooks up before you fully activate that queen-side knight.

Of course, he did later on have the promising continuation mentioned in #3...

Wow, nice, I think I would have been too worried about my queen rook's non-participation leading to me wasting time and allowing some counterplay.   Something like 20.b3 Rab8 21.Bd2 c4 and it's messy.

Instead you went straight ahead with it and found Nxg5.  At 25.g5 you're in great shape (as you say).  Pretty interesting game.  I thought black should try for center / queenside stuff asap after his rooks were connected and you were certainly contemplating a kingside attack... although like black I didn't think it looked very menacing at all until boom, Nxg5.  He took an even slower approach by maneuvering his bishop to f7.

I don't really understand 26.g6 though 27...Nxf5 surprised me, but even just 27...Bg8 and I don't know what white was planning.

You played very well IMO, it sucks to lose a game like this.  We all suffer heart breakers if we continue to play.  It's heartening to me when I see GMs throw away games too.

I think I'd prefer 27... Be8 (so the B isn't boxed in).

That may be true.  I kept looking at c4 for black the whole game, so I wanted to be able to play that :p

I'm a Grand Prix player and when you play Bxc6 the plan with kingside pawnstorm is incorrect. You're supposed to play Na4 and blockade the doubled c pawns . You also play the pawn break e4-e5 to take away the d6 base. Here is one example:

Of course, my opponent wasn't that high rated, he made a lot of mistakes. But you get the basic plan.  I didn't get to play Na4, c4, but I did manage to play e5 which is really important in that variation

Actually that may be a good lesson here.  With g5 black likely thought he was closing it up and limiting your attack to 1 file.  Meanwhile his queenside play looked pretty fast.

But it turned out g5 was a target, and maybe the black queen Qb6 was bad because it left the kingside too vurnerable?

10.g4 announces white's intentions, seems black's general idea should be to keep the pawn tension, finish development, and look for a way to open in the center or queenside.  Perhaps a principled reply to Nh4 is simply 11...c4.

Oh, and the post above me says an interesting alternative for white, to not go for a kingside attack with g4 at all, and focus on the queenside.

What happends after 22...fxg5? Maybe im blind but I couldnt see anything concrete other than two passed pawns.

22... fg 23 Qxg5+ Kf8 24 Qf6

It seemed to work out pretty well in the game (and against a FM). 

i dont see this as a tough loss bc you did not have a huge material or positional advantage if anything you played very agressively pushing kingside pawns inviting an early mate.  youre a much better player so i cant say much i suppose other than i dont see how this is such a tough loss?