Here is the full list of all 18 LEGO Brawls achievements.
Master the Mummy Queen Champion
Create 3 custom brawlers
Be named Top Brawler 20 times
Win 5 consecutive Brawl matches
Master the NRG Nya Champion
Play 20 Brawls
Be named Top Brawler 5 times
Play 5 games in Party Mode
Play your first game in Party Mode
Play 5 Brawls
Play your first Brawl
Be named Top Brawler
Customize your Loadout
Customize your first Brawler
Master the Cowgirl Champion
Master the Janitor Champion
Master the Owen Grady Champion
Master the Punk Pirate Champion