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