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