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