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