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