I wonder what Sersi could do to a dude that can punch planets.
She's absolutly powerful, but I can't see her in the top tier, like Thor, Surfer, Beta Ray Bill, Quasar, Nova Prime, Black Bolt, Hercules, Hulk and Gladiator.
She's not in the top tier like Hercules? You mean the guy who she physically manhandled and then one also one shot KO'ed? Nevermind she has shown that she can transmute Thor's body by giving him gills, so she can probably transmute Herc too. She can fly, she can turn all the air around hercules into water and drown him, encase him in an adamantium shell which he would have no way out of. Teleport him away. She can reform from being reduced to less than atoms. Really, what can Hercules do to her?
As for Black Bolt, all she has to do is transmute that tuning fork on top of his head.
Her shields have blocked a universe buster. Even if she doesn't use it in time, she can reform after being destroyed. Plus she can mind rape him. She has too many options.
There's no way to make an argument for Hercules over sersi. She beats him in his primary power, not to mention the 100 other powers she has.
The best argument for gladiator over sersi is speed, but I don't think it's enough to beat her. Definitely not permanently. And she can use weakness exploitation to end him rather easily unless he can one shot her some how.
If a 10-count KO constitutes a win, then Gladiator speed-blitzes and knocks her out easily before she can process a thought.
But if you mean who can actually kill or permanently put down the other, Sersi has too great of a control over her physical structure and can reform herself, so eventually she should be able to mind rape or transmute him for the win.