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