How to completely delete an app

[StormCrownSC]

How to properly uninstall an application to reinstall from scratch?

[sebres]

It depends on package manager / distribution.
For debians it'd be apt remove --purge fail2ban (see #3327 (comment) for details).

If you installed it manually (e. g. from source), it would be enough to remove:

?/usr/local?/bin/fail2ban-* /usr/local/lib/python3.*/dist-packages/fail2ban-* /etc/fail2ban /usr/share/doc/fail2ban

but better inspect the output of dry-run setup, for instance:

python setup.py --dry-run install --without-tests