noun
person who is a pain without realizing it; oblivious nuisance
Colloquial, mildly mocking term for someone who causes trouble or irritation but seems unaware of it. Often used affectionately or in exasperation.
彼はまた遅刻して、本当に困ったちゃんだ。
He's late again—what a pain, and he doesn't even realize it.
あの困ったちゃんには、何度言っても伝わらない。
No matter how many times you tell that oblivious nuisance, it never gets through.