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.
Find each member of the missing research teams.
Kill all Protozoans in the Borderworld.
Don't use the Cyanogen and let the Gonarch live.
Use Cyanogen to kill Gonarch.
Escape the Gargantua’s Lair without taking any damage from Gargantuas.
Find the snack supply canister.
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.
Complete Interloper without taking any laser damage.
Deliver the finishing blow to Gonarch with your Crowbar.
Kill 10 Enemies with Tripmines.
Help the Barnacle and Headcrab find true love.
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.
Kill 10 enemies with Snarks.
Conduct all of the questionable research experiments.
Overcharge it anyway.
Kill a Marine with their own grenade.
Assemble all the possible Scientists and Guards at the end of Office Complex.
Kill 10 Airborne Headcrabs using the Shotgun.
Use the alternate path in Office Complex.
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.
Use an entire clip of Gluon ammo in one continuous shot.
Don't kill any Vortigaunts in the Borderworld.
Kill a Controller without killing any of its mind-controlled Vortigaunt slaves.
Kill a Headcrab using fire.
Get whacked into oblivion in the ledge fight.
Drown in Lambda Core's coolant.
Kill an Icthyosaur with either the Tau or Gluon.
Kill 5 enemies with one grenade.
Kill a Barnacle with a Satchel.
Kill 20 enemies with the Hivehand.
Cook a Grenade for too long.
Get killed by your own Snarks.
Headshot 20 enemies with the .357 magnum.
Perform surgical caffeine extraction from 20 machines.
Kill an Assassin with the .357 Magnum.
Get overtaken by a Headcrab's ample anterior.
Kill 10 enemies with a reprogrammed Sentry.
Pass the toilet paper to the scientist in need.
Ruin the microwave casserole.