There is no global way, and thats because there also packages and stuff used by multiple Desktops, and also you may use applications from other DE… But you have the package groups:
sudo pacman -Rns plasma-meta kde-applications-meta
will do the job mostly >> it is better to do this in the terminal not inside pamac-gui!
what means the -Rns ??
R = remove
n = pacman saves important configuration files when removing certain applications and names them with the extension: .pacsave. To prevent the creation of these backup files use the -n option
s = To remove a package and its dependencies which are not required by any other installed package.
After this take a look that the Desktop environment you want to use is still installed:
xfce4 xfce4-goodies groups > for Xfce
cinnamon > for Cinnamon.
You can simple reinstall them or take a look with:
pacman -Qs xfce4
[updates once a week] = [90% less problems]
how to add system logs:
wget http://bit.ly/2GCG9k2 && sh 2GCG9k2
:handshake: donate antergos