Use this trick to bulk delete your old repos or old forks
Open in a new tab all to-be-deleted github repositores (Use the mouse’s middle click or Ctrl + Click) https://github.com/username?tab=repositories
Use one tab https://chrome.google.com/webstore/detail/onetab/chphlpgkkbolifaimnlloiipkdnihall to shorten them to a list.
Save that list to some path
The list should be in the form of “ur_username\repo_name” per line. Use regex search (Sublime text could help). Search for
\|.*and replace by empty.