Here is the full list of all 54 Serious Sam 4 achievements. It takes around 15-20 hours to unlock all of the achievements on Windows.
Make 20 enemies kill each other using Psychotropic Grenades.
Kill 20 enemies while dual wielding double shotguns.
Find out what happened to the English airman.
Escape the Oil Rig.
Send Mental a message he won't forget.
Beat the game on any difficulty.
Unlock 10 S.A.M.s in a single playthrough.
Navigate the citadel of Carcassonne. Start reassembling your team.
Get justice. Get the Holy Grail. Get screwed over.
Melee a big enemy.
Use the mininuke to eliminate 100 enemies at once.
Kill 11 different enemies using melee attacks.
Kill a Witchbride using C4.
Dismember 50 enemies with cannonballs.
Save a princess. Doesn't get more classic than that.
Go on a date with Hellfire.
Finish a text adventure. On an oil rig. During an alien invasion.
What if you could talk to the monsters?
Protect humanity's treasures from invaders with no taste.
Achievement is your middle name.
Spend 1000 minigun rounds while firing continuously.
Harvest 100 enemies with a combine harvester.
Assist a couple of young ladies out hunting.
Kill 50 healthy Kleers with a direct double shotgun hit.
Kill an Aludran Reptiloid using nothing but a pistol.
Cross the French countryside and get very cross.
Discover Fulbert's great invention.
Don't fear the reaper. Be the reaper.
Destroy 10 propaganda drones.
Ride the Popemobile to victory.
Kill a Belcher using Belcher collateral barf damage.
Meet a powerful granny.
Assist Dr. Vermetti in his war on worms.
One-shot kill 3 Werebulls with a shotgun.
Make sure Gabriella is OK.
Party like it's 199.
Sign Secchi's rifle.
Kill 5 enemies during a single Time Warp slowdown.
Head into Rome. Ditch Rodriguez.
Get a weaponized black hole, using science.
Kill 100 enemies with a headshot.
Run away from an angry volcano you foolishly antagonized.
Collect scorched aliens for Professor Kiesel.
Die HAARP With A Vengeance.
Recover the alien artifact located by Dr. Stein.
Kill 3 enemies with a double shotgun blast.
Find out what happened to Alessandro.
Recover a key stolen by a cultist.
Kill 5 enemies in a row while your health is below 10 HP.
Get together with your friends and kill something big.
Fight alongside Massimo Murena.
Unlock a S.A.M.
Save the rookie. Find Father Mikhail. See the sights.
Get knocked on the head and remember how you got here.