Here is the full list of all 30 Headcrab Frenzy! achievements.
Win 50 matches.
Exterminate 5000 hallucinogenic headcrabs.
Exterminate 4500 ethereal headcrabs.
Exterminate 4000 electric headcrabs.
Exterminate 3500 poison headcrabs.
Exterminate 3000 ice headcrabs.
Exterminate 2500 fire headcrabs.
Exterminate 2000 fast headcrabs.
Exterminate 1500 generic headcrabs.
Beat the game on "Hard" skill level.
Regenerate 100,000 health points.
Beat the game on "Medium" skill level.
Miss 1000 times.
Beat the game on "Easy" skill level.
Complete "HCF_Temple" arena.
Complete "HCF_Factory" arena.
Spend 60 minutes in Frenzy mode.
Complete "HCF_Range" arena.
Shoot 500 headcrabs using firearms.
Don't be bitten at all during a single wave.
Score 1,000,000 points in a single match.
Complete "HCF_Labmoar" arena.
Survive 20 waves in "Random" game mode.
Perform 250 nice catches.
Complete "HCF_Dungeon" arena.
Complete "HCF_Killbox" arena.
Survive 20 waves in "Ladder" game mode.
Perform a 25x combo.
Survive all 8 "Ladder" waves.
Cause some disorder in the Museum.