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.
Send Mental a message he won't forget.
Beat the game on any difficulty.
Kill 11 different enemies using melee attacks.
Escape the Oil Rig.
Kill 50 healthy Kleers with a direct double shotgun hit.
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.
Make 20 enemies kill each other using Psychotropic Grenades.
Kill 20 enemies while dual wielding double shotguns.
What if you could talk to the monsters?
Achievement is your middle name.
Destroy 10 propaganda drones.
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.
Harvest 100 enemies with a combine harvester.
Ride the Popemobile to victory.
Spend 1000 minigun rounds while firing continuously.
Kill 5 enemies in a row while your health is below 10 HP.
Meet a powerful granny.
Assist Dr. Vermetti in his war on worms.
Make sure Gabriella is OK.
Kill a Belcher using Belcher collateral barf damage.
Party like it's 199.
Head into Rome. Ditch Rodriguez.
Kill 5 enemies during a single Time Warp slowdown.
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 an Aludran Reptiloid using nothing but a pistol.
Recover the alien artifact located by Dr. Stein.
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.
Save the rookie. Find Father Mikhail. See the sights.
Kill 3 enemies with a double shotgun blast.
Get knocked on the head and remember how you got here.
Unlock 10 S.A.M.s in a single playthrough.
One-shot kill 3 Werebulls with a shotgun.
Melee a big enemy.
Use the mininuke to eliminate 100 enemies at once.
Kill 100 enemies with a headshot.
Kill a Witchbride using C4.
Sign Secchi's rifle.
Find out what happened to the English airman.
Assist a couple of young ladies out hunting.
Save a princess. Doesn't get more classic than that.