spit on (someone's) grave

Translations
плевать на могилу (кого-то)
He was so angry with his enemy that he said he would spit on his grave.
Он был так зол на своего врага, что сказал, что плюнет на его могилу.
Definitions
To show extreme disrespect or contempt for someone who has died, often by criticizing or insulting their memory or legacy. The phrase can be used literally (to actually spit on a grave) or figuratively (to speak or act in a way that dishonors the deceased).