Zuko being unnecessarily violent.
Note that Iroh stops Zuko when he can. Interestingly, in the example from “The Beach,” it’s not until Zuko pushes Ruon-Jian into the vase that Mai finally puts an end to things. This is likely due to Iroh having more experience dealing with Zuko’s temper.
Furthermore, while Iroh gets Zuko to stop, it’s only Mai that explains to Zuko what problematic behaviors he is displaying:
Mai: Your temper is out of control. You blow up over every little thing. You’re so impatient and hotheaded and angry!
However, I should probably note that, while Zuko’s temperament is reduced by the time of the comics, this behavioral change is due more to the context of the events in the show v the comics, rather than Mai’s verbal reprimands and Iroh’s physical intervention.