The Fight Trophy
You played a Voice Battle.
This is the only trophy in the game that actually requires 2 microphones. The game refuses to load without the second microphone and kicks you back to the main menu before you get chance to play anything.
With that in mind, the first thing to do is plug your second microphone in. Now go to Main Menu > Party > Voice Battle. Choose whichever song you’d like to hear. The setting doesn’t matter, make sure that (difficulty) is on Easy and for this trophy, song length doesn’t matter so change (song length) to Short.
Aim the fan or sing into microphone 1 only - position microphone 2 elsewhere so it has no input. While this isn’t essential, it gives Player 1 an early victory, making the trophy go quicker.
Now simply press to begin the Battle. Player 1 will win and when they do, after pressing to acknowledge the victory, the trophy will unlock on the loading screen.