vengeful and cruel
vindictive - mean
Somebody described as being ‘vindictive’ is considered to be acting in a deliberately malicious way against a person or group they feel has done them harm. The word is used in a negative and disapproving sense, not only because it implies cruelty and an inability to forgive, but also because such behaviour is often entirely unjustified.
I didn’t think I was a vindictive person, but when my boss fired me I found myself shamefully hoping that some harm would come to him.
Janice is spreading malicious rumours about me out of sheer vindictiveness because she is still angry that I broke up with her.
When I refused to withdraw my accusation against the politician, he vindictively tried to ruin my career.