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