"Dance on someone's grave" is a phrase that can quite easily offend people, as it implies that a person is hoping for their enemy's demise so they can celebrate their death. However, there are many alternative phrases that can be used in order to convey the same sentiment without resorting to such crass language. Some examples could include - "Revenge is a dish best served cold", "What goes around comes around", "Karma will catch up with them", or simply wishing them a "taste of their own medicine". These phrases and many others like them can convey the same message without using a phrase as disrespectful as "dance on someone's grave".