く悔kuやむyamu
1.
To feel deep regret or sorrow after realizing that a different course of action would have led to a better outcome, often reflecting on past mistakes.
2.
To express sorrow or sadness over someone's death, conveying feelings of loss and sympathy for the bereaved.
Example:
あの方があんなに若くして亡くなったことは悔やまれます。