If like me, you work across multiple repos, you've undoubtedly created a branch on the wrong repo, so annoying! Deleting the branch at first seems like tapping into the matrix. However, it's super easy if you know the right command, and here you go:

git push origin --delete <branch_name>

Also, if you've already checked this out locally, you can run:

git branch -D <branch_name>

You're most welcome...