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