A person’s apology matters less than the behavior that eventually makes apologies unnecessary.

Apologies are necessary and they are the beginning of the work rather than the completion of it. What matters far more is the gradual change that means the same apology stops being needed, because the behaviour itself has altered. Frequent apologising for the same thing is a sign that nothing has moved. The absence of the problem is the real repair.

Measure change by how often the incident recurs rather than by how well it is addressed afterwards. Say this plainly if you need to. Someone genuinely working on something will usually welcome that standard.