How to say "Regret" in Japanese

When translating "regret" into Japanese, you must choose carefully between 遺憾 and 会稽. In Japanese, 遺憾 (いかん (ikan)) is typically associated with "regret; pity; deplorable; highly regrettable; unsatisfactory" (Syllabus Level: N3) and represents Refers to deep regret, pity, or feeling deplorable/unsatisfactory about a bad result, accident, or diplomatic dispute. On the other hand, 会稽 (かいけい (kaikei)) maps to "regret, remorse, self-reproach" (Syllabus Level: N1) and represents 過去の失敗や過ちを深く反省し、後悔する気持ちを表す、やや硬い表現です。自己への批判的な視点を含みます。/ A somewhat formal expression for deeply reflecting on past failures or mistakes and feeling remorse. It includes a critical self-perspective.. A literal translation of "regret" can often sound unnatural to native Japanese speakers if mixed up!