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.
Regenerate 100,000 health points.
Exterminate 3000 ice headcrabs.
Exterminate 2500 fire headcrabs.
Exterminate 2000 fast headcrabs.
Exterminate 1500 generic headcrabs.
Spend 60 minutes in Frenzy mode.
Miss 1000 times.
Perform 250 nice catches.
Beat the game on "Hard" skill level.
Beat the game on "Medium" skill level.
Shoot 500 headcrabs using firearms.
Don't be bitten at all during a single wave.
Survive 20 waves in "Random" game mode.
Beat the game on "Easy" skill level.
Complete "HCF_Factory" arena.
Complete "HCF_Temple" arena.
Complete "HCF_Dungeon" arena.
Complete "HCF_Labmoar" arena.
Complete "HCF_Range" arena.
Complete "HCF_Killbox" arena.
Survive 20 waves in "Ladder" game mode.
Score 1,000,000 points in a single match.
Survive all 8 "Ladder" waves.
Perform a 25x combo.
Cause some disorder in the Museum.