anguish
答えの出ない問題に苦悶し続けた。
I continued to agonize over a problem with no answer.
彼は将来への不安から苦悶の日々を送っている。
He spends his days in anguish due to anxiety about the future.
苦悶の末に彼女は大きな決意を固めた。
After much anguish, she steeled her resolve.