How do I remove XFCE from my computer?

Try this

sudo apt-get purge xfconf xfce4-utils xfwm4 xfce4-session xfdesktop4 exo-utils xfce4-panel xfce4-terminal  thunar

followed by

sudo apt autoremove

Try these

sudo apt-get -f install
sudo apt-get clean
sudo apt-get autoclean
sudo apt-get update

Now

sudo apt-get purge xfce4

In my case (Mint with cinnamon and XFCE) I did:

sudo apt-get -f install
sudo apt-get clean
sudo apt-get autoclean
sudo apt-get update

THEN:

sudo apt-get purge xfce4  # failed

THEN:

sudo apt-get purge xfconf
sudo apt-get autoremove
sudo apt-get -f install
sudo apt-get clean
sudo apt-get autoclean
sudo apt-get update