Post rose Meruem>Adult Gon>Pre rose Meruem imo.
I must disagree.
At pre-rose, Meruem still had the brains, while Gon would just jump straight at the king. Watching Netero's abilities, Meruem found an opening, knowing he wouldn't be able to touch Netero without finding the opening in that Budda.
In power, Gon and Pre rose meruem are equal Imo, but they have different abilities. The only thing Gon has and Meruem doesn't, is his jan-ken, but it wouldn't surprise me if Gon has to use a lot of time to get one big enough to kill Meruem, while Meruem has 2 advantages:
1- He's smart af, and after testing one of gon's normal punches, then he wouldn't jump right into him, decreasing the possibilites of him getting hit by janken. Analyzing the fight, Meruem would find the perfect oppening (janken charge time) and finish Gon
2- If in that brutal fight, Meruem loses an extremity, Gon just gains the phisicall advantage. On the other hand, if Gon loses an extremity, Meruem uses his ability (specialization), eats that extremity and gains more Aura.
IMO, adult gon is really dangerous for meruem and could leave him in a critical state, but not kill him. With a linear moveset like his, i don't see him trapping Meruem. For me is:
Post rose Meruem > Pre rose >= Gon
