The title might be a bit misleading, but one of the things that Leah doesn't really know how to do in an active engagement is lose. With a creative mindset and the ability to think rather fast on his feet, he hasn't lost very much in his life. Sometimes in arguments with adults and other bits and pieces like not being able to put his thumb against the wrist of the same hand in line with the bone, but that isn't really loosing as much as fighting against a limitation you need to hurt yourself to overcome.
So in essence, this is someone who really doesn't know quite how to stop that escalation of a fight once it has started which isn't a good trait for the most part. You need to know how to stop once it's gone too far, unfortunately Leah right now will more then likely transfigure thermite and banish it at people then actually outright put his wand down and give up. This isn't the eradication of this flaw in one sitting, but if someone has some thoughts about slapping him down into the dirt or has some issues with that sort of thing with their own characters.
Well, I'm open to thoughts on the subject really. It's pretty open season at this point, the character is pretty fresh in terms of age and creation.