[[ As a general rule…
Overt Aggression, Quick to Anger, Violence as the First Option, Eager to/Willing to Kill over small infractions, any true belief that he’s dominant/better than people (especially if you add due to Uchiha heritage).
It’s one thing to be honest about his acting in Akatsuki– that’s fine, he was putting up an act, but when you’re writing Itachi outside of that or before that you can’t just make him some blood-hungry trigger happy person. He isn’t like that.
Also, any Itachi that acts (outside of Akatsuki again) as if Sasuke doesn’t exist or Sasuke is a burden. He died for Sasuke, his whole plan was with Sasuke in mind. You can’t just make him act like Sasuke’s some annoying sibling he’d rather get rid of. ]]

