"I forgive you," should never be followed by "but" or advice. The statement is enough, if sincere; move on. Thanking for the apology might be good, though.
I cannot grant forgiveness because I have moral superiority. I cannot grant forgiveness because I haven't done something as bad. I can't grant it because of tit for tat.
I can only grant it because I am forgiven for much worse by God. Grace for grace. That is the parable of the unjust steward, the world's most concise sermon on forgiveness