Karma is well-known throughout the school for his violent behavior and troublesome attitude. When he was in the main building, due to the betrayal of his most-trusted homeroom teacher, he began to hate all people who called themselves 'teachers' and as a result has almost zero respect for any adults. He is shown to be skilled in fighting, tricky, and manipulative, and takes great pleasure in harming others. He excels at using weaponry and foul play and is one of the few students thus far to have successfully injured Korosensei.
Karma has been described by Karasuma as "at first glance, he comes across as being a lazy sort, but... there's a strong sense of mischief in his eyes." Karma is quite relaxed most of the time as he occasionally skips out on things he finds boring, such as the school assembly. When fighting, he becomes brutal and has no qualms of hurting people who threatens him or any of his friends from Class E.
It is also shown that he is one of the most intelligent people in the entire school, shown to be ranked 4th out of all 186 students in Kunigigaoka. He does not, however, want to return to the main building, stating that he finds assassination much more interesting.
Regardless of his lazy personality, Itona has stated that Karma was probably the strongest within the class despite him not excelling in any particular area (shooting, knifework, etc). Most likely this means that Karma prefers to stick to tricks and pranks for assassinations rather than going into full-out combat, and also because of a certain "vision" Itona described to Terasaka. It has been mentioned by Karasuma, and proven many times, that Karma likes to humiliate his opponent.
Despite all this, Karma actually has good morales behind his motives. The reason he was placed in Class E was because he had rescued a senior from Class E being bullied by students from the main building. He was, unlike his classmates, unprejudiced against them and still considered the senior a 'senpai'.
He's also shown to be hardworking when he wants to by studying diligently after the embarrassing exam arc although he hides it by making it look like he was playing video games.
(Source: Assassination Classroom Wikia)
