These are achievements earned by killing specific enemies.
Savior of Sheep
Kill the Chupacabra at the Jensen's farm.
One Man's Junk
Kill Loki in the Junk Fortress.
Project Control Manager
Kill Project 432 in Dry Flats.
Thrilled to Deathspore
Kill the Deathspore of Needle Eye.
Cast a Deep Shadow
Kill Casta Gaunt in Old Kingman Prison.
Purge the Plateau
Kill 5 bosses of the Plateau.
Kill Geiger in Redfield.
One Ugly Mother
Kill Mother Larissa in the Catacombs at Sunset Hill Cementery.
Kill Professor Eddings at New Flagstaff University.
Kill the Union Blockade Commander near Kristo's Rest.
Better the Devil You Know
Kill Kenyon Holger in the Devil's Own Fortress.
Kill 5 bosses of Northfields.
Corazon Del Cadejo
Kill El Cadejo in the Brigg's Point Mine.
Rule the Roost
Kill Karaul Seung in Raven's Roost.
Feeling No Porkupain
Kill Porkupain near Docuer's Court.
Kill Serpent Trainer in the Human League Recruitment Center.
Kill Taylor Bartnev in Displacer Compound.
Clean Up Kaibab
Kill 5 bosses of Kaibab Forest.
Slayer of the Earth
Kill the Earthwalker of Gritstone Pit.
Kill Graham Winters in the LifeNet pod near Los Alamos.
Kill the Radiation-crazed Chupacabra in Deadfall.
Kill Venom of Terminal Woods.