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