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