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