To be clear about one's gratitude and grudges; to know whom to repay for kindness and whom to hold accountable for wrongs.
他是个恩怨了了的人，对帮助过他的人总是铭记在心，对伤害过他的人也绝不姑息。
He is a person who is clear about his gratitude and grudges; he always remembers those who helped him and never tolerates those who harmed him.
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