恩仇 is a literary compound that pairs 恩 (favor, kindness) and 仇 (enmity, grievance) to capture the full spectrum of interpersonal debts — both the good and the bad. It often appears in the set phrase 恩怨情仇 (favor, grievance, love, and hate) and in martial-arts or historical narratives where characters navigate complex relationships of gratitude and revenge. You won't hear it in everyday conversation; it belongs to written Chinese, especially fiction, drama, and formal commentary.