If you describe someone's language or behaviour as vitriolic, you disapprove of it because it is full of bitterness and hate, and so causes a lot of distress and pain.
"an acerbic tone piercing otherwise flowery prose""a barrage of acid comments""her acrid remarks make her many enemies""bitter words""blistering criticism""caustic jokes about political assassination, talk-show hosts and medical ethics""a sulfurous denunciation"
2. of a substance, especially a strong acid; capable of destroying or eating away by chemical action