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.
Regenerate 100,000 health points.
Exterminate 2000 fast headcrabs.
Shoot 500 headcrabs using firearms.
Survive 20 waves in "Random" game mode.
Beat the game on "Hard" skill level.
Exterminate 1500 generic headcrabs.
Beat the game on "Medium" skill level.
Spend 60 minutes in Frenzy mode.
Perform 250 nice catches.
Miss 1000 times.
Beat the game on "Easy" skill level.
Complete "HCF_Killbox" arena.
Score 1,000,000 points in a single match.
Complete "HCF_Dungeon" arena.
Complete "HCF_Labmoar" arena.
Perform a 25x combo.
Complete "HCF_Range" arena.
Complete "HCF_Factory" arena.
Survive 20 waves in "Ladder" game mode.
Don't be bitten at all during a single wave.
Complete "HCF_Temple" arena.
Survive all 8 "Ladder" waves.
Cause some disorder in the Museum.