grievance
1. [ noun ] (law,criminal law) an allegation that something imposes an illegal obligation or denies some legal right or causes injustice
Related terms: allegation
2. [ noun ] a resentment strong enough to justify retaliation
Synonyms: grudge score
Examples:

"holding a grudge" "settling a score"

Related terms: resentment stew
3. [ noun ] a complaint about a (real or imaginary) wrong that causes resentment and is grounds for action
Related terms: complaint