Rancorous

[Sarah]

Full of rancor; evincing, or caused by, rancor; deeplymalignant; implacably spiteful or malicious; intensely virulent.So flamed his eyes with rage and rancorous ire. Spenser.

[Renato]

having or showing a feeling of hate and continuing anger about something in the past:

[Luis Fok]

Characterized by bitterness or resentment.

[MiguelANymn]

showing deep-seated resentment

[Donald Trump]

Rancorous refers to exhibiting intense bitterness, resentment or malice. It describes a deep-seated ill will or hostility.

[TimothynTep]

Malignant; malicious; spiteful in the utmost degree.