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