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Achievements
507 hidden until unlocked
Average Unlock Rate
14%of owners, per achievement
Rare (Under 5%)
1530% of the list
Rarest
2%Pepperoni Precipitation
Most Common
61%Brownian Motion
By Rarity| Unlocked by | Achievements | Share |
|---|---|---|
| Under 1% | 0 | |
| 1–5% | 15 | |
| 5–20% | 23 | |
| 20–50% | 10 | |
| 50% and over | 2 |
All Achievements| # | Achievement | Unlocked |
|---|---|---|
| 1 |  Brownian MotionPass the toilet paper to the Scientist in need. | 61% |
| 2 |  Convection RefinementRuin the microwave casserole. | 50% |
| 3 |  Gray Matter PropulsionHeadshot 20 Enemies with the .357 Magnum. | 37% |
| 4 |  Prophylactic SuggestedGet overtaken by a Headcrab's ample anterior. | 33% |
| 5 |  Anti-Matter Over MindKill a Controller without killing any of its mind-controlled Vortigaunt slaves. |
Share of the game’s Steam owners who unlocked each achievement, checked 12 Nov 2026. Steam counts owners who never played, so rates run low. How we count
| 28% |
| 6 |  Premature ExpulsionUse an entire clip of Gluon ammo in one continuous shot. | 27% |
| 7 |  Inflammatory ActionsKill a Headcrab using fire. | 26% |
| 8 |  Limitless PotentialAccept G-Man’s offer of employment. | 25% |
| 9 |  Permeable InfrastructureUse the alternate path in Office Complex. | 23% |
| 10 |  Dead ReckoningKill an Assassin with the .357 Magnum. | 23% |
| 11 |  Centripetal AttractionKill 20 Enemies with the Hivehand. | 23% |
| 12 |  Caffeine ExtractionPerform surgical caffeine extraction from 20 vending machines. | 21% |
| 13 |  Well-DoneCook a Grenade for too long. | 19% |
| 14 |  Quantum CapacitanceOvercharge it anyway. | 19% |
| 15 |  Mega HertzKill 5 Enemies with one Grenade. | 19% |
| 16 |  Rather an AnticlimaxDecline G-Man’s offer of employment. | 17% |
| 17 |  Proverbial TinkererInterfere with the alarm and laptop in Anomalous Materials. | 16% |
| 18 |  Less Than Desirable ConsequencesDie in the AMS Beam before starting the experiment. | 16% |
| 19 |  Calculated TrajectoryKill 10 airborne Headcrabs using the Shotgun. | 14% |
| 20 |  Nuclear Fishin'Kill an Ichthyosaur with either the Tau or Gluon. | 12% |
| 21 |  PhD in PacifismDon't kill any Vortigaunts in the Borderworld. | 12% |
| 22 |  Remote DetonationKill a Barnacle with a Satchel. | 11% |
| 23 |  Contest PropellantHidden | 11% |
| 24 |  Stealth TechnologyEscape the Hangar in Surface Tension without alerting the Soldiers. | 11% |
| 25 |  Universal GravitationGet killed by your own Snarks. | 11% |
| 26 |  Resonance ProcrastinatorRefuse to insert the specimen into the Anti-Mass Spectrometer. | 10% |
| 27 |  Digital WizardryKill 10 enemies with a reprogrammed Sentry. | 9% |
| 28 |  Futile ResistanceKill 10 Enemies with Snarks. | 7% |
| 29 |  Unified Coupling TheorumHelp the Barnacle and Headcrab find true love. | 7% |
| 30 |  One Step AheadKill 10 Enemies with Tripmines. | 6% |
| 31 |  Kinetic RepulsionKill a Marine with their own Grenade. | 6% |
| 32 |  Hyper Saturation ConundrumDrown in Lambda Core's coolant. | 6% |
| 33 |  Gonad GliderGet whacked into oblivion in the ledge fight. | 6% |
| 34 |  Our Brains And Your BrawnAssemble all the possible Scientists and Guards at the end of Office Complex. | 5% |
| 35 |  Ethically QuestionableConduct all of the questionable research experiments. | 5% |
| 36 |  xen whenHidden | 5% |
| 37 |  Following the RulesHidden | 4% |
| 38 |  Orbital TrajectorySkip the opening Xen island with a secret jump. | 4% |
| 39 |  Black Mesa Decathlon WinnerEscape the Gargantua’s Lair without taking any damage from Gargantuas. | 4% |
| 40 |  Late for WorkDefeat Nihilanth in under 4 minutes. | 3% |
| 41 |  Doctor’s SignatureDeliver the finishing blow to Gonarch with your Crowbar. | 3% |
| 42 |  Specimen GGTake out all three Healing Crystals in Nihilanth’s Chamber at the same time. | 3% |
| 43 |  Rare SpecimenSend the Hidden Hat to Xen. | 3% |
| 44 |  The PlanHidden | 3% |
| 45 |  Laser ImmunizationComplete Interloper without taking any laser damage. | 3% |
| 46 |  Unquestionably EthicalHidden | 2% |
| 47 |  Post-Mortem IntervalFind each member of the missing research teams. | 2% |
| 48 |  The Rarest SpecimenHidden | 2% |
| 49 |  Prolific PopperKill all Protozoans in the Borderworld. | 2% |
| 50 |  Pepperoni PrecipitationHidden | 2% |
Black Mesa Relive Half-Life.
