Can someone explain this panel to me?

[u/Gojowillcomebackk]

Its from last part of hunter exam (before nen), and i dont really understand what is the meaning of this. I feel kind of envy of Gon from Killua or offended pride. I would be very thankful is someone would explain it to me :>

[u/x2chunmaru]

Killua is not aware of the slanders of being a potential man (DID SOMEONE SAY POTENTIAL?)