I guess he's in what I call the meta human range. Around Ironman levels but below the lowest cosmic characters like Heralds or Magneto. Strongest character he could beat? Hmm. Probably the likes of Abomination or Super Skrull with relative ease and most versions of Ironman. But the strongest, it's hard for me to think of someone that would push Toriko and at the same time not be stronger. He's in that between low herald and above city level threats like Hulk. Only Hulk is still a bit stronger.
Toriko can defeat Super Skrull at his best with ease?
Mid-high tier avenger. Iron Man with 2% shields can tank a nuke, Toriko wont get past that or any other guys that surpass Iron man. Even some versions of Gambit and night crawler would be able to win. Sometime it's not about who could make the biggest mushroom cloud that determines a character's ranking, Toriko as a whole barley has any hax in his verse, Toriko himself has non with the exception of his precog. But low-mid tier characters like Rogue, Gambit (I think he may be omega level though) and Nightcrawler have always fought people bigger, stronger, and more durable than they are. And almost any telepath should be able to take him down as well. That's why he would be about high-low tier in Marvel, characters with like over 100 characters with 70+ years of feats.
Conduct of the King is pretty hax. But I get your point. Although Toriko can beat some versions of Ironman, I'm not saying he could beat Extremis, Thor buster or even the current 616 version. The Classic, former 616, maybe original bulk buster armors he should be able to beat. But on the comment that said low mid tier mutants, for the most part thats false. He isn't beating Omega or some alpha mutants but most every other mutant he could beat easily telepaths aside. Even some of them with precog he could take out before they invaded his mind. Toriko is by no means low tier in Marvel. Id say upper mid tier in the grand scheme of things if you consider the likes of Ironman or Namor upper mid tier.
Marvel has hundreds of characters with large amounts of hax abilities and years of feats and consistencies to back them up. I'm by no means saying toriko is weak but if you consider the levels of hax required for some mid tier marvel characters toriko falls short in that department. I'd give him low mid tier at best.