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