A list I delete keeps reappearing after sync

Mac app first

Some sync capabilities mentioned here, such as Merge sync and Todoist, are currently available in 2Do for Mac and are coming to the iOS app in an upcoming update.

Another device still has the list and is pushing it back up. Delete the list on all devices, then sync. If the list still reappears after deleting it from every device, it may also exist on the sync service itself (iCloud CalDAV, another CalDAV server, Toodledo, or Todoist) — delete it from that service's web interface as well. If you sync with Apple Reminders, delete the corresponding list in the Reminders app.