What does a sincere apology consist of?

For example: somebody says “When you said/did this, it upset me.”
If the persons response is to act confused, list off reasons why you shouldn’t be upset, ask why you’re upset over something menial, topping that off with “I’m sorry you feel hurt.”
Does that sound sincere to you?
In my opinion, someone telling me they feel hurt by my actions is enough. They shouldn’t have to explain themselves. If I know I said something that hurt someone close to me, I’d take responsibility and genuinely apologize.
What does a sincere apology consist of?
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