*EDITED DUE TO FEEDBACK (thanks to EverStoned77)*
Go to Brawl Night, choose fight "7 Champ - Ryan Johnson"
At the character select screen, highlight Felipe Cruz.
You don't have to fight as it will pop as soon as you start
When you go to Brawl Night & then select Champ 6 Gabriel Ribeiro you get sent to another character select screen that AFAIK have all the fighters so simply find the one you need, in this case Felipe Cruz, start the fight & before your opponent break your jaw the achievement pops