I remember the King only winning due to his experience with Komugi. Meruem didn't have a Hatsu too. I see Adult Gon beating the King due to his Hatsu, but Gon lacks the experience with calculations, predictions, making a plan, etc... that Meruem learned from battling Komugi in Gungi, which made him win the battle.
Gon would try to hit Netero, but would fail. He would get pummeled, but due to his emotion state, I don't think he would feel pain. Meruem felt dull pain after many many strikes, but I don't think Gon would feel any pain in that state. I don't know if the Buddah can deflect, or even intercept a Jajanken Pa, but by that time, I think Gon can slip by and get the chance to kill Netero. Meruem didn't want to kill Netero because he wanted to learn his name. I'm certain a Jajanken Gu will deflect anything the Buddah throw at him. I don't know what would it do to Zero Hand, but I'm sure he'll survive that, and kill Netero.
If Netero had the bomb here, I see Gon still surviving this. Meruem at the time didn't utilize his full defenses, while Gon is a master of Ken. He could even use Gyo, making his frontal side have more aura than the back side.