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.
Get justice. Get the Holy Grail. Get screwed over.
Go on a date with Hellfire.
Dismember 50 enemies with cannonballs.
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.
Cross the French countryside and get very cross.
Kill a Witchbride using C4.
Kill 50 healthy Kleers with a direct double shotgun hit.
Discover Fulbert's great invention.
Don't fear the reaper. Be the reaper.
Destroy 10 propaganda drones.
Harvest 100 enemies with a combine harvester.
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 20 enemies while dual wielding double shotguns.
Assist Dr. Vermetti in his war on worms.
Make sure Gabriella is OK.
Party like it's 199.
Kill an Aludran Reptiloid using nothing but a pistol.
One-shot kill 3 Werebulls with a shotgun.
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.
Kill 5 enemies in a row while your health is below 10 HP.
Collect scorched aliens for Professor Kiesel.
Die HAARP With A Vengeance.
Recover the alien artifact located by Dr. Stein.
Kill a Belcher using Belcher collateral barf damage.
Kill 100 enemies with a headshot.
Find out what happened to Alessandro.
Recover a key stolen by a cultist.
Get together with your friends and kill something big.
Fight alongside Massimo Murena.
Unlock a S.A.M.
Kill 3 enemies with a double shotgun blast.
Save the rookie. Find Father Mikhail. See the sights.
Get knocked on the head and remember how you got here.
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.
Melee a big enemy.
Kill 5 enemies during a single Time Warp slowdown.
Use the mininuke to eliminate 100 enemies at once.
Kill 11 different enemies using melee attacks.
Make 20 enemies kill each other using Psychotropic Grenades.
Finish a text adventure. On an oil rig. During an alien invasion.