Here is the full list of all 31 Pummel Party achievements.
Accidentally blew yourself up in the 'Strategic Shockwave' minigame
Place last in every minigame
Died in 'Acidic Atoll' throwing a barrel
Got hit by the train in 'Temporal Trails'
Get launched off screen in 'Tunneling Tanks'
Steal the last gift in a players pile in 'Grifting Gifts'
Complete 'Gift Grab' without collecting coal
Complete 'Slippery Sprint' without falling in the water
Hit three players with the remote control eggplant
Win 'Magma & Mages' without taking damage
Survive in 'Breaking Blocks' for 60 seconds
Place first in every minigame
Complete 'Rusty Racers' without falling off the track
Control over 50% of the area in 'Elemental Escalation'
Knockout 10 players in one game of 'Explosive Exchange'
Find the treasure in 'Sandy Search'
Score over 5 in 'Bouncing Balls'
Get a 5 player kill sreak in 'Speedy Sabers'
As the lightning holder kill every other player in 'Thunderous Trench'
Collect 40 keys in 'Winter Maze'
Skewer three players with the rocket skewer item
Get a double kill in 'Barn Brawl'
Survive for at least 50 seconds in 'Sorcerers Sprint'
Knock off 5 players in one game of 'Snowy Spin'
Start your first game
Win your first game
Take no damage in 'Searing Spotlights' minigame
Survive for 50 seconds in 'Bullet Barrage'
Get your first goal
Win your first minigame