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.
Send the Hidden Hat to Xen.
Assemble all the possible Scientists and Guards at the end of Office Complex.
Deliver the finishing blow to Gonarch with your Crowbar.
Get whacked into oblivion in the ledge fight.
Skip the opening Xen island with a secret jump.
Conduct all of the questionable research experiments.
Kill 10 Enemies with Tripmines.
Kill 10 enemies with a reprogrammed Sentry.
Kill a Marine with their own grenade.
Drown in Lambda Core's coolant.
Refuse to insert the specimen into the Anti-Mass Spectrometer.
Die in the AMS Beam before starting the experiment.
Kill an Icthyosaur with either the Tau or Gluon.
Get killed by your own Snarks.
Cook a Grenade for too long.
Help the Barnacle and Headcrab find true love.
Kill an Assassin with the .357 Magnum.
Overcharge it anyway.
Escape the Hangar in Surface Tension without alerting the Soldiers.
Kill a Barnacle with a Satchel.
Interfere with the alarm and laptop in Anomalous Materials.
Kill a Headcrab using fire.
Kill 5 enemies with one grenade.
Decline G-Man’s offer of employment.
Accept G-Man’s offer of employment.
Use an entire clip of Gluon ammo in one continuous shot.
Don't kill any Vortigaunts in the Borderworld.
Kill a Controller without killing any of its mind-controlled Vortigaunt slaves.
Kill 20 enemies with the Hivehand.
Kill 10 enemies with Snarks.
Perform surgical caffeine extraction from 20 machines.
Kill 10 Airborne Headcrabs using the Shotgun.
Use the alternate path in Office Complex.
Pass the toilet paper to the scientist in need.
Headshot 20 enemies with the .357 magnum.
Get overtaken by a Headcrab's ample anterior.
Ruin the microwave casserole.
Kill all Protozoans in the Borderworld.
Carry the Hidden Hat to Endgame.
Use the welcome mat.
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.
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.