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.
Conduct all of the questionable research experiments.
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.
Die in the AMS Beam before starting the experiment.
Refuse to insert the specimen into the Anti-Mass Spectrometer.
Interfere with the alarm and laptop in Anomalous Materials.
Accept G-Man’s offer of employment.
Decline G-Man’s offer of employment.
Don't kill any Vortigaunts in the Borderworld.
Use an entire clip of Gluon ammo in one continuous shot.
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.
Help the Barnacle and Headcrab find true love.
Kill an Icthyosaur with either the Tau or Gluon.
Kill a Barnacle with a Satchel.
Escape the Hangar in Surface Tension without alerting the Soldiers.
Get killed by your own Snarks.
Kill 10 Enemies with Tripmines.
Overcharge it anyway.
Kill a Marine with their own grenade.
Cook a Grenade for too long.
Kill a Headcrab using fire.
Drown in Lambda Core's coolant.
Kill 20 enemies with the Hivehand.
Kill an Assassin with the .357 Magnum.
Kill 10 Airborne Headcrabs using the Shotgun.
Get overtaken by a Headcrab's ample anterior.
Headshot 20 enemies with the .357 magnum.
Use the alternate path in Office Complex.
Perform surgical caffeine extraction from 20 machines.
Pass the toilet paper to the scientist in need.
Ruin the microwave casserole.
Kill 10 enemies with Snarks.
Send the Hidden Hat to Xen.
Kill all Protozoans in the Borderworld.
Carry the Hidden Hat to Endgame.
Wait too long to jump into the Lambda Teleporter.
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.
Complete Interloper without taking any laser damage.
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.