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