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.
Kill 10 enemies with a reprogrammed Sentry.
Kill 10 Enemies with Tripmines.
Kill 10 enemies with Snarks.
Kill all Protozoans in the Borderworld.
View the *other* secret ending.
Defeat Nihilanth in under 4 minutes.
Escape the Gargantua’s Lair without taking any damage from Gargantuas.
Carry the Hidden Hat to Endgame.
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.
Find the snack supply canister.
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.
Get whacked into oblivion in the ledge fight.
Cook a Grenade for too long.
Use the welcome mat.
Kill an Icthyosaur with either the Tau or Gluon.
Skip the opening Xen island with a secret jump.
Send the Hidden Hat to Xen.
Wait too long to jump into the Lambda Teleporter.
Get killed by your own Snarks.
Overcharge it anyway.
Drown in Lambda Core's coolant.
Escape the Hangar in Surface Tension without alerting the Soldiers.
Kill an Assassin with the .357 Magnum.
Kill a Barnacle with a Satchel.
Help the Barnacle and Headcrab find true love.
Kill a Marine with their own grenade.
Assemble all the possible Scientists and Guards at the end of Office Complex.
Use the alternate path in Office Complex.
Perform surgical caffeine extraction from 20 machines.
Kill 10 Airborne Headcrabs using the Shotgun.
Kill 5 enemies with one grenade.
Kill a Headcrab using fire.
Refuse to insert the specimen into the Anti-Mass Spectrometer.
Die in the AMS Beam before starting the experiment.
Interfere with the alarm and laptop in Anomalous Materials.
Accept G-Man’s offer of employment.
Decline G-Man’s offer of employment.
Headshot 20 enemies with the .357 magnum.
Kill a Controller without killing any of its mind-controlled Vortigaunt slaves.
Use an entire clip of Gluon ammo in one continuous shot.
Kill 20 enemies with the Hivehand.
Conduct all of the questionable research experiments.
Get overtaken by a Headcrab's ample anterior.
Pass the toilet paper to the scientist in need.
Ruin the microwave casserole.