Why is this a blunder?

Chessis suggests that after bxf4 I just scoot my king to b1 and gxf4 after the queen runs away. Is it just because I'm left with doubled isolated pawns? Does seem like they'd be impossible to defend...

Proud of this one! Find the mate in 2, White to play

Played drunk with friend and I was down a queen and still won. We’re both rated around 1200

Promotion to knight is best move?

I did this as a joke at first, then the engine said it was the best move.

I’ve got my first Brilliant. 3 to be exact. I still don’t know why.

Won a game - opponent had zero mistakes & blunders

I'm quite proud of myself. Can't remember I ever beat someone who did not even make a mistake.

Didn’t even see that I technically sacrificed my bishop as well

Gothamchess would be proud of my move here

To be fair I didn't calculate this all the way. This came out of the "boring" London system opening.

I JUST BEAT NELSON

I finally managed to reach 2000 puzzle elo

Best next move?

I am black