Here is the full list of all 34 Screencheat achievements.
Kill an Opponent inside a vent on the Manor
Reach level 50
Kill 1 opponent from each coloured area in Helix
Kill someone in the hill when they have 1 second to win
Harpoon 2 players in one shot with the Trappeur
Play 5 games with 4 local players
Get a multi-kill from beyond the grave with the Bearbomb
Get a double kill with a returning Sörgeån
Get a quad-kill including yourself
Get 4 kills without reloading the Revolver Rifle
Kill an opponent inside the center tunnel on Loop
Reach level 25
Kill 3 opponents from behind with the Candelabra
Play 20 rounds in a row in Party Mode
Spend 10 seconds off the ground without dying on Holy Mountain
Kill an opponent through multiple objects with the wall_Hacker
Spend over 75% of a round charging with the Hobby Horse
Win a round of Murder Mystery without being killed
Get a multi-kill in One Shot
Play a perfect round of deathmatch with the Blunderbuss
Win a round without ever missing a shot on Temple
Reach level 5
Kill 5 Opponents from on top of the dinosaur in the Museum
Stay in one place in the Garden for 1 minute
Get a quad kill or more with a single Chefolet ball
Fire 50 grenades in Hill Campers and win
Get a mutli-kill with a projectile weapon through a vent
Get 1 kill with each weapon in a round
Kill 5 players from the moving platforms on Steeple
Get 3 kills whilst bouncing on the floating cushions.
Win a round on Ascension in less than 30 seconds with the default mode settings
Get a Bronze medal or higher on all training missions.
Get a Silver medal or higher on all training missions.
Get a Gold medal on all training missions.