Here is the full list of all 41 Warhammer 40,000: Shootas, Blood & Teef achievements.
Killed 10 Genestealer Cultists
Killed 10 sewer enemies
Defeated The Bastion of Valor
Defeated the Leman Russ
Killed 1 Commisar
Defeated the Boss Nob
Killed 10 Astra Militarum
Killed 10 Orks
Defeated The Patriarch
Defeated Lord Horrik Canorem, Son of High King Valorik Canorem, High Prince of House Canorem, Master of the Blade of Gaia, Keeper of the Gates of Loralo, Wielder of the Kaloric Flame, Bringer of Hope, Herald of the Holy Order of the Adamantine Lance, The Paladin of Koto, Slayer of the Lion of Essa, The Triumphant! The Light of Stars! The Eradicator!
Defeated Warlord Gutrekka
Completed all levels on hard
Defeated the Biophagus
Defeated the Killakan
Defeated the invictor warsuit
Defeated the Chaplain
Defeated the Sentinel
Defeated the genestealer
Defeated the Genestealer Duo
Didn't consume ammo 1000 times as Flash Git
Used Storm Dash to bash enemies 200 times
Killed 200 enemies by throwing the Beast Snagga spear.
Shocked 200 enemies as the Weird Boy
Meleed an ally 100 times
Killed 100 enemies with grenades
Killed 100 enemies with melee attacks
Entered WAAAGH! 100 times
Consumed 200 squigs
Found all secrets hidden troughout the game
Killed 20 Commisars
Killed 5 Tempestus Scions
Killed 75 Tempestus Scions
Killed 1 Space Marine
Killed 25 Space Marines
Killed 500 Orks
Killed 500 Astra Militarum
Killed 500 sewer enemies
Killed 500 Genestealer Cultist
Bought every hat in the store
Bought every weapon in the store
Completed all other achievements