The show starts off pretty tame at first but gets more mature as it goes on, with the Chapter Black Saga being the darkest of them all. There's a fair bit violence with blood, as well as a disturbing flashback focusing on mankind's horrible deeds like torture and murder
Kurama decapitated a teenager controlled by young toguro. Its pretty bloody.
During a fight,hiei cut off his own arm in order to kill an enemy. The scene is brutal
Toguro massacred the tournament committee. It's really graphic and violent. He killed one by flicking his finger making his head explode.
Toguro pirece kuwabara hearts and blood starts pouring out.
Sensui witness yokai being tortured by human beings. He then proceeds on killing every humans in the torture room. Pretty bloody
Karasu tortures kurama by surrounding him with bombs. Kurama is left in a bloody state
Hei cuts off a person's arm. Blood is seen coming out. And then proceeds stabbing his opponent through the head.
Doctor kamiya got his arm blasted off by yusuke.
There is a lot of supernatural animated violence, which can get pretty graphic. The main characters confront enemies by punching, stabbing, supernatural attacks (which can lead to disintegration), decapitations, amputation, and explosions. There is also a fair amount of animated gore during fights.
Some of the violence is bloody, with episode 63 being the bloodiest of the entire series.
Lots of martial arts/action.