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