English Translation
They are bitter enemies.
Is 仇 properly きゅう, あだ, or かたき?
EDICT has two variants:
仇同士 [かたきどうし] (n) mutual enemies
仇同士 [てきどうし] (ik) (n) mutual enemies
The (ik) marker means “irregular kana usage”, so I guess that means that かたき is the more common variant.