Cleaning up old remote git branches

Consider to run :

git fetch --prune

On a regular basis in each repo to remove local branches that have been tracking a remote branch that is deleted (no longer exists in remote GIT repo).

This can be further simplified by

git config remote.origin.prune true

this is a per-repo setting that will make any future git fetch or git pull to automatically prune.

To set this up for your user, you may also edit the global .gitconfig and add

[fetch]
    prune = true

However, it's recommended that this is done using the following command:

git config --global fetch.prune true

or to apply it system wide (not just for the user)

git config --system fetch.prune true

First, what is the result of git branch -a on machine B?

Second, you have already deleted heads/devel on origin, so that's why you can't delete it from machine B.

Try

git branch -r -d origin/devel

or

git remote prune origin

or

git fetch origin --prune

and feel free to add --dry-run to the end of your git statement to see the result of running it without actually running it.

Docs for git remote prune and git branch.