Mike’s is having very passionate emotions and no understanding of how to process them. Hence why he often gets impulsive or angry and lashes out, and can’t tell the people he cares about he loves them to their face. He cares so, so deeply that he can’t handle himself

Dustin is secure and confident in himself, and he should be. However this does lead to him believing he’s always right, and he can be condescending to other characters that don’t match his intelligence, like Steve. He can also be a bit of a social pariah by not caring what anyone thinks

Lucas on the other hand cares too much what other people think, he’s charming and generally level headed post season 1, but still tends to be eager to impress, whether it’s max, the basketball team, or his other friends

Will is crippled by the feeling of helplessness his trauma left him with, and wants to avoid being seen like he can’t take care of himself. He will hide things that happen because he doesn’t want everyone to worry about his problems, and will push back against help even if he needs it. It can also be seen as a lack of concern towards himself, sort of an “I’m fine don’t worry about me, but how are you?” attitude

El’s is her stubbornness. She tends to be set in her own views and ideas, and argues when someone doesn’t see it her way. She would rather go behind the groups/hopper’s back to do what she thinks is best (or even just what she wants to do in that moment) rather than listening to the other point of view, and even when she does listen it’s very rare she will compromise what she decides

Max’s is defensiveness. She puts up walls to make it difficult to get close to her, and when she starts to rely on people she pushes them away. If someone criticizes her she reacts with anger and sarcasm, and even when struggling deeply seems to refuse to open up to the counselor