The bodyguards can't act recklessly because their boss is not the brother, it's the two's father, so if they take side and the loser complain to their father they risk getting fired for mistreating their boss' kid.
Safest bet for them is to let the brothers fight and at worst get scolded by the losing brother.
Then for the strength, even the weak can do damage, human bodies aren't made of steel, anyone that played fight with a kid that doesn't know how to control their strength can tell you that. Getting sucker punched hurt even if you could overpower the one hitting. X)
If he really was so important, he wouldn't have been treated badly by his brother. He could have just complaint to his father. And it's not like they are harming him, they can just hold him back. + Can't the brother side with them and just say that they were protecting him ( which they should as bodyguards) from the mc cuz he was going crazy and attacked him.
Sucker punch might hurt but you have to be really fcking weak if you can't punch back + he looks well build, he can take few punches especially from someone who is a lot weaker.
That is just chinese manhua logic where Mc can beat a villian 10 times stronger than them in a weak malnutritioned body they just transmigrated into. ╮(￣▽￣)╭
Even if he was being mistreated by his own siblings, that's pretty normal in a family. Siblings fight and parent would careless but will still get angry if something bad happen to them that weren't cause by their own fam.
MC's body old owner probably a pushover who let people do things to him. And I have this hunch that's probably the only reason why his sibling keep bullying him.
I'm not saying they beat him up at least hold him back. Like do there job as a bodyguard.
One thing that bugged me the most is that he is going around beating people with no consequences. Like ok I get he was a gangster but still the body he is in is weak, with low stamina. How is grown ass alpha getting beaten by him ( I will let the first encounter slide because he had a gun) and those body guards, they can still hold MC back without harming him. ( I like to imagine that they didn't help that alpha brother because they wanted him to get beaten lol)