I had something that was ridiculously large, I've already followed some of the guides that recommend disabling the repositories and uninstalling games which i've done. Surprisingly, one game took up something like 80MB... and I don't even have doom installed.

I think this should remedy the issue, but for some reason I cannot run the apt-get clean and apt-get autoremove commands once i've run the SUDO GAINROOT command to gain root access. Is there another way to gain root access?