spiteful - nasty
If you are ‘spiteful’ then you set out to deliberately upset, undermine, or harm somebody because you dislike them or feel that they have wronged you in some way. With spiteful people, their actions are typically unwarranted or over the top, and they tend to feel little or no remorse.
Instead of explaining his issue with me face-to-face, Tom went straight to the boss and tried to have me fired. He is a truly spiteful person.
My manager has spitefully blocked my promotion because we have had a number of disagreements in recent weeks.
The couple’s divorce was far from amicable. In fact, there was a high degree of spitefulness involved on both sides.