What do you consider a good apology?

I was fired up last night (which continued on to this morning) and decided to type up some apology 'letters' for the friends that I let down and hurt. I just put all my feelings down and didn't let myself get bogged down by grammar and sentence structure in the way I would have done in the past. I've talked about how bad I felt, the things I realise were hurtful to them and how much I want to do better.

I tried to approach it from a perspective of "I'll write this to get my feelings down but I won't send it". Maybe I will one day, but I do fear that it will make things worse.

I reached out to a few a couple months ago but didn't hear back. Probably because the message I wrote was so pathetically vague that it didn't display any actual learning. It was literally me going "I really valued our friendship and would be keen to have a conversation".

For you as an individual, what do you consider to be an apology that you would accept?