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