Complete TFE, TSE or BFE single player campaigns on unmodified serious difficulty.
Trigger Ugh-Zan's regeneration on The Great Pyramid.
Pull out a single Colt and immediately deliver a killing shot.
Kill 20 enemies with the Minigun without releasing the trigger.
Pierce at least 10 enemies with a single cannonball.
Leap into the unknown on Luxor.
Complete any level in single player.
Cut down some trees.
Find a secret under water.
Use the Flamethrower on a Lava Golem.
Destroy an enemy cannon with your own cannon.
Complete Serious Sam: The First Encounter
Survive the storm on the Grand Cathedral.
Kill at least 30 enemies with a single Serious Bomb.
Kill 100 enemies with Serious Damage active.
Complete the South America episode in single player or cooperative.
Complete the Persia episode in single player or cooperative.
Complete the Medieval episode in single player or cooperative.
Earn a gold medal on any level in single player Survival.
Finish the Legend of the Beast campaign in single player or cooperative.
Rescue professor Stein. So to say.
Secure the bird.
Finish Serious Sam: The Second Encounter
Decipher an Egyptian text.
Defeat the spaceship.
Kill an enemy using the Mutilator.
Solve the riddle of the Sphynx.
Kill an enemy with a gib torn from another enemy.
Kill a Witch-Bride of Achriman.
Kill the kicked enemy while it is still in the air.
Power up the Timelock.
Start the car.
Find Sam's classic outfit.
Complete Serious Sam 3: BFE
Awake the Guardian of Time.
Rip Scrapjack's head off.
Blow a Major Biomechanoid into pieces.
Use the Mutilator to surf after a Werebull.
Complete the Jewel of The Nile single player campaign.
Find at least 30 secrets in single player.
Kill at least 5 headless kamikazes in one explosion.
Kill 10 enemies with the Chainsaw without releasing the trigger.
Kill 50 Cucurbitos.
Squash 10 Hatchling spiders.
Obtain the Air Element.
Gib 20 enemies from close range with a shotgun.
Kill at least 3 enemies in one spinning Sledgehammer attack.
Obtain the Earth Element.
Obtain the Fire Element.
Obtain the Water Element.
Defeat the Lava Golem boss on Alley of the Sphinxes.