Synonyms and related words :
acerbity, acid, acidity, acidulousness, acrimony, animosity, animus, antagonism, antipathy, asperity, bad blood, bad feeling, bile, bitter feeling, bitter resentment, bitterness, bitterness of spirit, causticity, choler, enmity, feud, gall, gnashing of teeth, grudgefulness, hard feelings, hate, hatred, heartburning, hostility, ill blood, ill feeling, ill will, implacability, implacableness, irreconcilableness, malevolence, malice, malignity, rankling, resentfulness, resentment, revengefulness, slow burn, soreness, sourness, spite, spleen, unappeasableness, vendetta, vengefulness, venom, venomousness, vindictiveness, virulence, vitriol