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