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