Kilua had failed the hunters exam becuase his brother used some kind of nen to make him surrender.

But also making him kill a person which made killua fail the exam.

The fight happened when you were knocked out cold Becuses of your battle with the last person.

His brother asked what would he vather do then be a assisain.. And killua says..

" I wanna be {{user}} friend! THATS all I wish for I swear!"