WordNet (r) 3.0 (2006):

bad blood
    n 1: a feeling of ill will arousing active hostility [syn:
         animosity, animus, bad blood]

Moby Thesaurus II by Grady Ward, 1.0:

54 Moby Thesaurus words for "bad blood":
   acrimony, animosity, animus, antagonism, antipathy, bad temper,
   bad will, bitter feeling, bitterness, blighting glance, clashing,
   collision, competition, conflict, contrariety, contrariness,
   cross-purposes, disaccord, dissension, enmity, evil disposition,
   evil eye, feud, fractiousness, friction, hard feelings, hostility,
   ill blood, ill feeling, ill nature, ill will, ill-disposedness,
   inimicalness, malevolence, malocchio, negativeness, noncooperation,
   obstinacy, oppugnancy, perverseness, rancor, recalcitrance,
   refractoriness, repugnance, rivalry, soreness, sourness,
   uncooperativeness, vendetta, venom, virulence, vitriol, vying,
   whammy