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