Well, for the brave
dpkg -l | awk '/.kde/{print $2}' | sed "s/:amd64//g" -> apt purge $( dpkg -l | awk '/.kde/{print $2}' | sed "s/:amd64//g")
Or save the important things like keys (ssh, rsa, pgp and so on) your private stuff ..., and install our xorg-iso, clean it and then install i3 and all the things you need,
But first test if it boots, the ISO!
Edit: and check for plasma dpkg -l | awk '/.plasma/{print $2}' | sed "s/:amd64//g"
Edit . Edit: this results in -> dpkg -l | awk '/.kde.|.plasma./{print $2}' | sed "s/:amd64//g"