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