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.
Skip the opening Xen island with a secret jump.
Refuse to insert the specimen into the Anti-Mass Spectrometer.
Die in the AMS Beam before starting the experiment.
Decline G-Man’s offer of employment.
Accept G-Man’s offer of employment.
Defeat Nihilanth in under 4 minutes.
Take out all three Healing Crystals in Nihilanth’s Chamber at the same time.
Complete Interloper without taking any laser damage.
Cook a Grenade for too long.
Find the snack supply canister.
Kill a Controller without killing any of its mind-controlled Vortigaunt slaves.
Kill an Assassin with the .357 Magnum.
Kill a Headcrab using fire.
Kill a Barnacle with a Satchel.
Help the Barnacle and Headcrab find true love.
Kill 10 Airborne Headcrabs using the Shotgun.
Kill 10 enemies with a reprogrammed Sentry.
Kill 5 enemies with one grenade.
Overcharge it anyway.
Use an entire clip of Gluon ammo in one continuous shot.
Get killed by your own Snarks.
Send the Hidden Hat to Xen.
Kill 20 enemies with the Hivehand.
Headshot 20 enemies with the .357 magnum.
Get overtaken by a Headcrab's ample anterior.
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.
Interfere with the alarm and laptop in Anomalous Materials.
Conduct all of the questionable research experiments.
Kill 10 enemies with Snarks.
Drown in Lambda Core's coolant.
Kill a Marine with their own grenade.
Kill an Icthyosaur with either the Tau or Gluon.
Kill all Protozoans in the Borderworld.
Don't kill any Vortigaunts 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.
Use the welcome mat.
Deliver the finishing blow to Gonarch with your Crowbar.
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.
Escape the Gargantua’s Lair without taking any damage from Gargantuas.
View the *other* secret ending.