:: Starting full system upgrade...
resolving dependencies...
looking for conflicting packages...
warning: removing 'nodejs' from target list because it conflicts with 'nodejs-lts-hydrogen'
:: nodejs-lts-hydrogen and nodejs are in conflict. Remove nodejs? [y/N] y
error: failed to prepare transaction (could not satisfy dependencies)
:: installing pacman (6.1.0-3) breaks dependency 'pacman<6.1' required by libpamac-full
-> error installing repo packages
error installing repo packages
pacman -Rc libpamac-full, in this case, will remove libpamac-full and what is dependent on it, namely, pamac-all, assuming that that is the package you installed from AUR.
You could also do pacman -Rs pamac-all, instead, to remove pamac-all and its dependency,
namely libpamac-full.
Be mindful of not using both options together as it has the potential to remove all of the dependencies of a certain package recursively and whatever is dependent on it recursively.
For more (and surely better) explanation of these options, please refer to man pacman.