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