How do I remove Steam?

You can use Ubuntu Software Center to uninstall or Open Terminal and execute the following command:

sudo apt-get remove steam steam-launcher

Purge Steam Perfectly with Configuration files with the following:

sudo apt-get purge steam steam-launcher

Never forget to delete its directory located at home folder:

rm -rf ~/.local/share/Steam && rm -rf ~/.steam

The .deb package is just a wrapper. Steam's launcher installs itself to ~/.local/share/Steam and can be over 1GiB so make sure you remove it.

sudo apt-get purge steam
sudo apt-get purge steam-launcher
cd ~/.local/share && rm -rf Steam
rm ~/.steampath
rm ~/.steampid

You may have only one of "steam" or "steam-launcher".