You need to login to do this. Thus, in typical TV-land logic, if you become psychotic, you must also become violent—even if you never were before. A character who already resorts to violence will turn on their friends instead of fighting whatever enemy they minecraft honeydew fight.
What’s more, the fictional psychotic will not only be invariably violent, they’ll actually be more lethally effective than a sane person. This is usually used to enhance the frightening aspect of a character, since psychosis makes them unpredictable and their behavior unfamiliar. In a fight, they have terrifying Confusion Fu. Very occasionally, this can be Truth in Television: people with mental illnesses do commit slightly more violent crime than average. But it’s not anywhere nearly as common as media would imply.
This is becoming more of a Discredited Trope, thankfully, as more writers are leaning towards interesting motives for violence, but still lingers on in the Horror genre. Compare it with Sanity Has Advantages. Contrast Loon with a Heart of Gold. Higurashi: When They Cry is full of this. Farfarello of Weiß Kreuz falls under this, particularly in back story. Taken to the extreme in Soul Eater.