viperous

/ˈvaɪpərəs/
adjective
  1. Having the qualities of a viper; venomous, treacherous, or spiteful.
    • She gave him a viperous look that made him step back.
    • The politician's viperous remarks during the debate shocked the audience.
    • The viperous gossip spread through the office, damaging many reputations.