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