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.
Shoot 500 headcrabs using firearms.
Exterminate 2500 fire headcrabs.
Regenerate 100,000 health points.
Exterminate 2000 fast headcrabs.
Exterminate 1500 generic headcrabs.
Beat the game on "Hard" skill level.
Beat the game on "Medium" skill level.
Miss 1000 times.
Spend 60 minutes in Frenzy mode.
Beat the game on "Easy" skill level.
Complete "HCF_Temple" arena.
Complete "HCF_Factory" arena.
Score 1,000,000 points in a single match.
Perform a 25x combo.
Don't be bitten at all during a single wave.
Cause some disorder in the Museum.
Complete "HCF_Range" arena.
Perform 250 nice catches.
Survive 20 waves in "Random" game mode.
Complete "HCF_Labmoar" arena.
Complete "HCF_Dungeon" arena.
Survive 20 waves in "Ladder" game mode.
Complete "HCF_Killbox" arena.
Survive all 8 "Ladder" waves.