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resentment; grudge; malice; bitterness
matter for regret; regret
彼への憾みはまだ消えていない。
My resentment towards him hasn't faded yet.
若い頃に留学しなかったことが憾みだ。
I regret not having studied abroad when I was young.
憾みを抱えたままでは前に進めない。
You can't move forward if you keep holding onto a grudge.