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