When someone says sorry but it's not okay?

When someone apologizes, i usually try to think of a going forward preventative measure, to share ownership. But if the issue is absolutely caused from someone's disregard / ignorance / inattentiveness, saying "it's okay" makes one a pushover. So how do you handle - not accept - someone's apology if it's not really okay?

Contrary of the tone of this question, im really not one to hold a grudge!

Aaaaand let the lectures on forgiveness begin 😆