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