When it comes to expressing the idea of anger, resentment, or animosity between people, the term "ill blood" is commonly used. However, there are other synonyms that can be used as well. For instance, one might also say "bad blood" or "sour relations" to describe a negative relationship between individuals or groups. Other close synonyms include "resentment," "hostility," and "antipathy." Whether you're trying to describe a personal feud or a tense political situation, having a strong vocabulary of synonyms to draw upon can be immensely helpful when choosing the right word to use.