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