i-adjective
doesn't learn their lesson; obstinate
Describes someone who repeats the same mistake or bad behavior without learning from experience. Often used in the phrase 懲りない人 or 懲りないやつ.
彼は何度注意されても同じ失敗をする、本当に懲りない人だ。
He makes the same mistake no matter how many times he's warned; he really doesn't learn his lesson.
あのチームは毎年同じ戦略で負けている
That team loses every year with the same strategy, but they never learn.