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