Here is the full list of all 50 Black Mesa achievements. It takes around 20-25 hours to unlock all of the achievements on Windows.
View the *other* secret ending.
Carry the Hidden Hat to Endgame.
Perform surgical caffeine extraction from 20 machines.
Use the welcome mat.
Send the Hidden Hat to Xen.
Wait too long to jump into the Lambda Teleporter.
Drown in Lambda Core's coolant.
Assemble all the possible Scientists and Guards at the end of Office Complex.
Complete Interloper without taking any laser damage.
Escape the Gargantua’s Lair without taking any damage from Gargantuas.
Find the snack supply canister.
Use Cyanogen to kill Gonarch.
Don't use the Cyanogen and let the Gonarch live.
Find each member of the missing research teams.
Kill all Protozoans in the Borderworld.
Help the Barnacle and Headcrab find true love.
Skip the opening Xen island with a secret jump.
Conduct all of the questionable research experiments.
Deliver the finishing blow to Gonarch with your Crowbar.
Get whacked into oblivion in the ledge fight.
Defeat Nihilanth in under 4 minutes.
Take out all three Healing Crystals in Nihilanth’s Chamber at the same time.
Kill 10 enemies with Snarks.
Escape the Hangar in Surface Tension without alerting the Soldiers.
Kill 10 enemies with a reprogrammed Sentry.
Kill a Marine with their own grenade.
Kill a Headcrab using fire.
Refuse to insert the specimen into the Anti-Mass Spectrometer.
Interfere with the alarm and laptop in Anomalous Materials.
Accept G-Man’s offer of employment.
Decline G-Man’s offer of employment.
Don't kill any Vortigaunts in the Borderworld.
Kill a Controller without killing any of its mind-controlled Vortigaunt slaves.
Get killed by your own Snarks.
Use an entire clip of Gluon ammo in one continuous shot.
Kill 10 Enemies with Tripmines.
Kill an Icthyosaur with either the Tau or Gluon.
Kill 20 enemies with the Hivehand.
Kill a Barnacle with a Satchel.
Headshot 20 enemies with the .357 magnum.
Overcharge it anyway.
Kill an Assassin with the .357 Magnum.
Kill 5 enemies with one grenade.
Kill 10 Airborne Headcrabs using the Shotgun.
Use the alternate path in Office Complex.
Cook a Grenade for too long.
Get overtaken by a Headcrab's ample anterior.
Die in the AMS Beam before starting the experiment.
Pass the toilet paper to the scientist in need.
Ruin the microwave casserole.