These were recently of use to me.

https://snew.notabug.io/
https://www.removeddit.com/
https://www.reveddit.com/

snew finds stuff that was moderated, but not posts and comments deleted by their own authors. The other two are far more effective on that regard. None of them can undelete images that were uploaded to i.redd.it.

Deliberately excluded: ReSavr (only stores long comments), Archive.org (does not focus on Reddit alone).