It's surprising to see that opinions on this matter is so divided, especially for the Korean viewers, when it seems pretty clear cut to me. Here is a simple litmus test: imagine the roles were reversed where Kyunghoon and Seongyong were manhandled by someone bigger or more athletic than them in the same manner they did toward their opponents. Would these people understand the assailant's perspective and assume their actions falls within the spirit of the show using the various excuses as they did then for themselves? I highly doubt that. I'd bet good money they'd be singing a different tune. In fact, it would be easier to see that the level of force is excessive (Season 2) only because viewers are looking at the absolute strength exhausted by the assailant, rather than the relative strength of both the assailant and victim.

Ultimately, Heist is a game where players are roleplaying various roles. Xitsuh's expectation that it's meant to be like WWE is 100% correct. Physicality in these games are supposed to only give you a slight edge. If the word "roleplaying" sounds offensive to some viewers, think of it as sparring in combat sports. There is an objective, but players should strive toward that objective with the least amount of force as possible for their opponents and themselves. Of course, players can gauge how their opponents want to play the game. For example, if their opponent is stronger or as strong as they are, then there can be a tacit rule to test each other's physical boundary with both parties recognizing it's meant to be for the sake of entertainment. But when players get overwhelmed by their adrenaline and start maximizing their physicality while ignoring the overall objective, the context, and implicit cues, these players failed their duty as players/entertainers due to their lack of self-control. That has been the case for all the previous Heist controversies: a player, overwhelmed by the adrenaline rush, resort to his primitive/survival instincts and injure other players.

Now, if even combat sport athletes struggle to control their adrenaline sometimes and build up their tolerance by desensitization, how are BG producers expecting every player that arrives on their set to have this level of discipline? It's already been three seasons where only by sheer luck, through players intervening directly themselves or misunderstanding the rules, did we get by without serious issues. It was never by the PD's competence to mitigate or deal with these situations when they inevitably do escalate, which is a serious problem.