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