I never read the comics so I cannot comment too much about them, although from what I do know of them, by scans I've seen posted from other people, I cannot say I like that version of Princess Celestia as it depicted her to be bullying toward her younger sister Luna for not learning magic as quickly as her. Considering that Princess Celestia was created to inspire friendship in her kingdom, it does seem out of character, why would a Pony, who wishes to inspire positivity and loyalty of her kingdom, do something like that? true, some Ponies were corrupt before they redeemed later on, but in Princess Celestia's case it just does not fit.
I'm not saying Princess Celestia has to be perfect either, even in the TV show, she does appear to have what some people may view as "crude and inappropriate humor" like her smiling about her pet Phoenix turning to ash though Phoenixes are immortal and Celestia is well aware of this, it is understandable why some people would think that way about Celestia, but given she has ruled Equestria for over 1,000 years, I would come to expect that of Celestia, why? because let's be honest, ruling a kingdom for such a long time would be very boring, for anyone, could I handle that pressure? no, if this were me, I would've retired long ago, I would not have the strength to rule a kingdom for 10 years, let alone 1,000. Not that it excuses Celestia in situations where she has made a mistake, however a job like that is very tough, from decreeing laws that are helpful, not just at a whim, to actively engaging with the public.
In the TV show, Princess Celestia's behavior is sometimes good, however there were clear signs of neglect toward her sister Princess Luna, unresolved issues that caused Luna to behave the way she did in Royal Problem. Princess Luna was not being "bratty" here, she made gestures of kindness toward others in Canterlot castle, like placing lavender around the place at night, and her gestures of kindness were seemingly forgotten about or ignored. I'd be upset too, if somebody else in my family kept behaving as if I did not exist and they did not have a good excuse for it, there comes a point where ignorance does become toxic. Even small acts of kindness, can mean a lot to somebody.
I've seen good criticisms of both Celestia and Luna, and some bad ones, but I would hardly call either of them "tyrannical", I've seen far worse behavior from royalty from other fictions, where their actions were much less redeemable or excusable.