Dead Age

The best place to find Wolves is in Woods Day/Night. The Woods, both Day and Night versions, are available right at the start of the game. Because Wolves are one of the earliest enemies encountered in the game, though in a harder area than the Highway, this may be the fourth or fifth "Kill" achievement you will unlock.

Only enemies labeled as "Darkwolf" or "Undead Wolf" count for this achievement.

Darkwolf Stats
Fast: Yes
Immune to K.O./Stun: No
High Defense (aka needs Breakthrough): No
Special Abilities: Vampiric Bite (Life Steal), Clamp Jaw (Self-Damaging)
Priority Targeting Level (1 - 8, 1 is max, 8 is min): 7
Locations: Woods Day/Night

Undead Wolf Stats
Fast: Yes
Immune to K.O./Stun: No
High Defense (aka needs Breakthrough): No
Special Abilities: Chilling Howl (Debuff), Debilitating Bite (Debuff)
Priority Targeting Level (1 - 8, 1 is max, 8 is min): 8
Locations: Woods Day/Night