Rings of Remorse
To some degree this isn't an apology more than it is self punishment.
I plan on getting myself custom bracelets for my legs. The thing is I don't plan on having something nice and delicate. They will be heavy encumbering magnetic weights.
Each time I will hurt someone I will clamp more rings on my feet. The more severe the damage done the heavier the burden I carry. Since it's magnets it won't come off easily, such as the feeling of guilt and remorse won't. And the heavier the ring, the harder it is to remove.
I will not even attempt removing them until the damage I caused will be fixed, so I will carry it with me all day for a long time.
Important note: It's not meant for small insignificant things where saying "I'm sorry" and being done with it will do. Only serious matters count.
You might ask how is this even an apology?
I would ask of you to think of a person you have hurt to a level you believe beyond redemption. Now imagine their reaction when they will realise you were walking for days with heavy weights on your feet dedicated to keeping them until you will fix the wrong you have done.