acerbity, acid, acidity, acidness, acidulousness, acridity, animosity, animus, antipathy, asperity, astringency, bad blood, bile, bite, bitingness, bitter feeling, bitter resentment, bitterness, bitterness of spirit, causticity, causticness, choler, corrosiveness, edge, feud, fierceness, gall, gnashing of teeth, grip, hard feelings, harshness, heartburning, ill blood, ill feeling, ill will, incisiveness, keenness, malevolence, malice, malignity, mordacity, mordancy, piercingness, poignancy, point, rancor, rankling, rigor, roughness, severity, sharpness, slow burn, soreness, sourness, spite, spleen, stabbingness, sting, stridency, stringency, tartness, teeth, trenchancy, vehemence, vendetta, venom, violence, virulence, vitriol