The God Of High School anime's first season allowed its fighters to take things to the next level in terms of sheer brutality. People who choose to participate in the show's tournament are injected with nanomachines that quicken their healing, along with monitoring their health during fights, and it's thanks to these machines that severe injuries can be recovered from in record time. In the latter portion of the tournament, more and more fighters rely on Charyeok powers to gain a helping hand from deities and warriors to increase the chance of these injuries -- or even outright fatalities. But this cruelty pales in comparison to that of an older tournament-based series, Shaman King.
When it comes to brutality in GOHS, Jegal is a prime example. In his first main fight of the tournament, he demonstrates his Charyeok's deadly potential, calling upon his megalodon that can either fire off individual teeth at opponents or chew them into a bloody mess. Jegal demonstrates in this fight, and subsequent ones, that he doesn't care about the people that he fights against. His philosophy boils down to the fact that he has to prove he is stronger than everyone else -- by any means. By defeating enemies and punishing the weak for their weakness, he affirms to himself that he is truly stronger than everyone else. In this first tournament fight, Jegal destroys his opponent, Jugok, completely one-sidedly. In fact, the only reason his opponent doesn't outright die is because Han Daewi interferes.
Jugok is humiliated in this battle but this isn't the last we see of his feud with Jegal. After he is hospitalized and granted the Greed Charyeok, Jugok encounters Jegal in the hospital and fights him once again. Here, Jugok seems to be able to last longer, until the moment that his maid enters the picture. She always tries to protect Jugok when he's in danger, but in this particular fight, she becomes a mere tool for Jegal to exploit by him savagely attacking her. This turns Jugok into a monstrous form, one which lets him absorb people to strengthen himself. Jegal eventually kills him, while also dismembering two of Ilpyo's friends in the process.
While Jegal is brutal with the way that he fights, there is a limit to the way that he goes about his schemes. He mostly fights those who either get in his way or who he has to defeat to fulfill his ultimate objective of becoming all-powerful. Within the world of Shaman King, though, there are opponents that will fight just as dirty if not dirtier in their quest to become the titular Shaman King. And there's no better example of how much certain shamans will bend the rules to gain victory than Faust VIII.
Before the official fight between Faust VIII and Yoh begins, he coaxes his opponent to exhaust himself by kidnapping his friend Manta. While Manta can see ghosts, he doesn't have the fighting potential that Yoh does. Manta is hung up on a cross of bones where Faust VIII proceeds to explain the experiments he wants to conduct on his victim. Using his abilities, Faust VIII sticks his hand inside of Manta's body, causing the boy immense pain as he touches his internal organs. And while Yoh is distracted with bone minions, Faust also expends a little furyoku manipulation to mess with Manta's brain, too. Due to all of this, Yoh struggles to fend off Faust's attacks when the time comes for their "official match" to start.
Perhaps one of the only reasons that Faust VIII doesn't fully lobotomize Manta right then and there is because of Yoh's provocations: insulting the doctor's work by regarding his wife, Eliza, as nothing more than a puppet. This causes Faust VIII to use his furyoku on Eliza to batter down Yoh with relentless attacks. Yoh does put up more of a fight than some expected, but in the end, he's knocked to the ground and almost finished off for good by Faust's final attack.
Faust is certainly maniacal but other fighters have also been considerably cruel in the world of Shaman King. Another example is Tao Ren, who kills Patch Chrom, one of the judges of the shaman fights, without any remorse.
Both series feature some shockingly torturous scenes, both during their respective tournaments and outside of them. The God Of High School's Chareyok powers can easily become tools of destruction in the wrong hands. However, while some of the fighters of that show aren't afraid to fight dirty, the matches in Shaman King are downright filthy in comparison.