$ sudo pip uninstall virtualenv 

WARNING: Skipping virtualenv as it is not installed.

$ sudo pip3 uninstall virtualenv 

WARNING: Skipping virtualenv as it is not installed.

$ sudo apt-get purge python-virtualenv  

Reading package lists... Done

Building dependency tree       

Reading state information... Done

Package 'python-virtualenv' is not installed, so not removed

0 upgraded, 0 newly installed, 0 to remove and 136 not upgraded.

$ virtualenv --version

virtualenv 20.4.3 from /home/manu/.local/lib/python3.8/site-packages/virtualenv/__init__.py

pip list and pip3 list mention the virtualenv.

Also, commands mentioned here do not work:

sudo apt-get remove virtualenv  

sudo apt-get remove --auto-remove virtualenv

sudo apt-get purge python-virtualenv  

sudo apt-get purge --auto-remove python-virtualenv