Yeah I think for me a Mary Sue is defined by player's inability to take criticism or allow their character to face consequences. You can make characters that are overly egotistical, overly powerful, or both work. But the key is to let them be genuinely flawed individuals. Realistically no one is going to want to be around someone who is so far up their own ass they never see the light of day. Eventually even the most patient individual is going to get sick of the attitude.I'm just sick of Mary Sues on so many levels. And the thing is, I have a really chill definition of what a Mary Sue is because I believe that Mary Sues come from bad writing, not inherently from power. Some characters are obscenely powerful, but are not Mary Sues because they're well-written and their power comes after their personality or is intertwined with their personality in a compelling manner. Other characters are Mary Sues because their excessive power/excessive amount of "special" qualities are a stand in for a personality.
But damn, I'm just so tired of "here are the 17 reasons why my character is special, none of which have anything to do with my writing ability ".
And power-hungry assholes are just that assholes. They aren't going to be well-liked and admired by everyone around them. Sure some people might cozy up if their the type to want to be near power. But not every person under the sun.
Which I think is a lot of times where the more "Mary Sue"-ish writing comes in. As it focuses on forcing a particular reaction from the audience to the character and it makes a character who can never be wrong/disliked/or given any kind of lasting flaws.
When in reality writing these people as flawed and shallow individuals is actually a lot more fun. It's like playing a villain, sometimes it's fun to just go over the top and let your character be the most hated person in the roleplay.