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