Is there a way to delete all stack exchange accounts at the same time?
I also want to remove all traces of my posts on the site. Is that possible?
Will I have to delete all of my posts manually?
Can I use the stack exchange API for this?
Fill out this form for each site, or at least leave a note in the "Reason" field explaining that you want to remove all of your accounts. You will still need to edit your profile on every site to say "please delete me".
Be prepared to provide an explanation for the site-wide nuking of all of your posted content; generally speaking, content you provide to the network belongs to the community, not to you (by posting it, you agreed to pledge it to the community via the Creative Commons license) and will not be removed.