Unless you want to argue that Graviton's cake-walking Thor and the avengers was anomalous (and the only feat that would go against this, as I've said, was against a weakened Graviton), then yes, he has been depicted at this level.
Really, though, I don't have enough free time to a do a battle-zone debate - posting as much as I do on here is a vice and guilty pleasure as it is.
As for Graviton vs. supes, the fact of the matter is that herald level force simply hasn't been effective against Graviton, and your iron man example is against a weakened version. Why are you so reluctant to admit this? It does not even change the outcome of this fight.
Probably because there's nothing to support the notion that Graviton is the most powerful character on the field, especially when multiple JLA'ers have more impressive feats.
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Not only multiple JLA'ers, but also Silver Surfer, Thor, Quasar, and even Magneto have superior feats. Now, given that I acknowledge this, ask yourself why I would still say that Graviton is the strongest on the field.
Though Graviton's feat of capturing and restraining every superhuman on earth at the same time across the planet and entirely out of visual range (including Genis, Thor, Hulk, Doop, Jean Grey, Vision etc), while simultaneously tearing out and levitating every major city across the the US and the world thousands of feet into the air, while also commencing to terraform the entire surface of the earth and carrying on casual conversations and fighting the Thunderbolts at the same time must place him up there as one of the most powerful.
Re: JLA vs. Graviton, Magneto, Sandman, Hydroman, Electro & Terrax
GAWD...
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A million words a second and I know your imperfections, baby
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