I have downloaded opera from the website (deb package) and installed it. Now I want to remove it but I don't know how. I tried
sudo apt-get remove opera but it didn't work.
When you install via the downloaded .deb binaries/installer and not the opera repository for Opera, then it was installed with
@Thomas W.'s answer didn't work for me on Ubuntu 14.04. I had to use:
And to remove the apt sources file added by Opera: