From Longman Dictionary of Contemporary Englishsettle a score/accountsettle a score/accountFINISH DOING somethingto do something to hurt or cause trouble for someone because they have harmed or offended you Did he have any enemies – someone with an old score to settle? → settle
Examples from the Corpus
settle a score/account• Schiavo certainly deserves no credit for scaring people needlessly just to settle a score.• Boudjema believes that the opposition parties are settling a score with the Socialist government and using the schoolgirls as a scapegoat. 