https://about.deviantart.com/policy/submission/ 3. License To Use Artist Materials. As and when Artist Materials are
uploaded to the DeviantArt Site(s), Artist grants to DeviantArt a
worldwide, royalty-free, non-exclusive license to do the following
things during the Term:
a) to prepare and encode Artist Materials or any part of them for
digital or analog transmission, manipulation and exhibition in
any format and by any means now known or not yet known or
invented;
b) to display, copy, reproduce, exhibit, publicly perform,
broadcast, rebroadcast, transmit, retransmit, distribute through
any electronic means (including analog and digital) or other
means, and electronically or otherwise publish any or all of
the Artist Materials, including any part of them, and to include
them in compilations for publication, by any and all means and
media now known or not yet known or invented ;
c) to modify, adapt, change or otherwise alter the Artist Materials
(e.g., change the size) and use the Artist Materials as described
in Section 3(b); and ...
The only thing a DeviantArt user can do is to delete their content, shut their account, and leave the site.
The policies only apply for the "Term" in which a user exists and the art exists on the platform.