Here's one. You should find it yourself.
It doesn't matter if it takes you an hour.
Keep trying.
Mate in one?
Sort:
Bg4 wins the queen.
Mate in one is Qe3
It says you missed black's checkmate, Qe3# or Ne4# 
Instead of where your pieces are, look at where they can go. Analyse the vacant squares too. As you can see, your king is paralyzed.
Keep practicing and analysing 
A checkmate must include a last check. That´s clear, I think.
So you have to have a look for checks, where the checking piece can´t be taken from a white piece (in this case) or let the King run away. The white King can´t move, so a check, that includes these conditions will win the game.
Here it is Qe3# or Nd4#. There are several other moves to check the white King, but they all faile: Bc3+ could be answered with bxc3, Be3+ let the king go out to d3 or c3, Qd3+ is countered with cxd3 as well as Qc3+ with bxc3. There are no other checks. That is the process of elimination.
archaja wrote:
A checkmate must include a last check. That´s clear, I think.
So you have to have a look for checks, where the checking piece can´t be taken from a white piece (in this case) or let the King run away. The white King can´t move, so a check, that includes these conditions will win the game.
Here it is Qe3# or Nd4#. There are several other moves to check the white King, but they all faile: Bc3+ could be answered with bxc3, Be3+ let the king go out to d3 or c3, Qd3+ is countered with cxd3 as well as Qc3+ with bxc3. There are no other checks. That is the process of elimination.
At my first blunder, there was a chance for a forced checkmate after several consecutive checks.
https://www.chess.com/analysis/game/live/57916760131?tab=review
Computer says i missed a mate in one, SEVERAL times, i thought the game went great, can you help me see the mate in one i missed?