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.
Find out what happened to the English airman.
Save a princess. Doesn't get more classic than that.
Melee a big enemy.
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.
Go on a date with Hellfire.
Dismember 50 enemies with cannonballs.
Navigate the citadel of Carcassonne. Start reassembling your team.
Kill 11 different enemies using melee attacks.
What if you could talk to the monsters?
Kill 50 healthy Kleers with a direct double shotgun hit.
Achievement is your middle name.
Protect humanity's treasures from invaders with no taste.
Cross the French countryside and get very cross.
Don't fear the reaper. Be the reaper.
Destroy 10 propaganda drones.
Make 20 enemies kill each other using Psychotropic Grenades.
Harvest 100 enemies with a combine harvester.
Assist a couple of young ladies out hunting.
Ride the Popemobile to victory.
Kill a Belcher using Belcher collateral barf damage.
Spend 1000 minigun rounds while firing continuously.
Meet a powerful granny.
Kill an Aludran Reptiloid using nothing but a pistol.
Kill 100 enemies with a headshot.
Assist Dr. Vermetti in his war on worms.
Kill 20 enemies while dual wielding double shotguns.
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.
Kill 5 enemies in a row while your health is below 10 HP.
Get a weaponized black hole, using science.
Run away from an angry volcano you foolishly antagonized.
Kill a Witchbride using C4.
Collect scorched aliens for Professor Kiesel.
Die HAARP With A Vengeance.
Recover the alien artifact located by Dr. Stein.
One-shot kill 3 Werebulls with a shotgun.
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.
Unlock 10 S.A.M.s in a single playthrough.
Use the mininuke to eliminate 100 enemies at once.