I made the unfortunate mistake of agreeing to be added as an AU on my mom's card, when I was attempting to help her establish and manage her credit.
She maxed out the card and it started dragging down my score, we're not on speaking terms so asking her to remove me was out of the question as she's spiteful enough to refuse just so that she can screw me. Luckily I found out from searching that an AU for Amex can remove themselves.
Que the happy dance.
I logged into my AU account and requested they close the card via chat. Whole process took about 24 hours to close it completely, it reported for a little bit as closed and then disappeared completely.
I'm glad I did as I just recently found out that one of her other cards got charged off.