illumi genuinely wanted to protect killua but it ended up being unconventional. the tactics were undeniably abusive, but illumi managed to shy killua away from danger. he never really meant any harm to killua it just ended up that way.
also no offense, but chrollo and hisoka are a lot shittier than illumi. illumi’s assigned to kill meanwhile hisoka does it for pure enjoyment and chrollo committed mass genocide for whatever reason. to think illumi is the worst out of the trio is really fucking dumb lol.
people treat killua like he’s an absolute angel and he means no harm to anyone ever, that he’s pretty much fragile - which is the opposite of his character. he has his ruthless moments and is by no means weak or fragile, stop treating him that way.
not only that, but people tend to forget that illumi was raised to be cold-blooded with no value for human life. people tend to forget that, yes, illumi was abused too. he had to take care of his siblings as well, which makes things harder on his end.
i’m not gonna get into it anymore than that but this is pretty much the bottom line of things.