I couldn’t agree more strongly on this point. Glasya-Labolas is an extremely intense spirit that genuinely fits the title of being a demon, in that he is one of deep darkness. But I will echo that this does not mean he’s malicious to the Sorcerer - far from it! He does seem to enjoy harming or killing the enemies of the Sorcerer when requested, though.
I recently asked him to kill someone I learned was a pedophile, and I trust that he will deliver.