Gladiator definitely has some HH showings. Gladiator was even created as one of the earliest (maybe the earliest??) Marvel versions of Superman (Strontians are basically Kryptonians, the race is almost extinct, Gladiator has a ‘superboy’ called Kid Gladiator and a ‘supergirl’ called Xenith, similar powers, and even his real name - Kallark - is quite similar to Clark). And he has some showings (eg his speed at times) that are genuinely some of the best anywhere.
He has one problem though - if the Marvel Pantheon of Characters was a SitCom then Gladiator would basically be an occasional guest star.
The likes of Spider-Man, Hulk, X-Men etc would be the main characters, the likes of Silver Surfer, Thanos, Dr Strange would be regular guest characters, but the likes of Gladiator, the Shiar, Adam Strange would be occasional guest characters.
Only showing up when there is a story that requires their involvement.
This means that for Gladiator - if the story requires a super powerful overwhelming force he will be there, but sometimes the story requires that super powerful overwhelming force to be defeated by Cannonball and knocked back by Gambit!!!! Bendis also really messed him up.
Anyway, the problem with ‘occasional guest characters’ is that they can easily be misused. Marvel will never mess up the Hulk in the same way DC will never mess up Superman or (the former Image and Wildstorm respectively) would never mess up Spawn and Mr Majestic. No imprint will never mess with its main characters.
But the occasional guest stars ....
So, that’s the problem for Kallark (and others like him, eg Count Nefaria etc) - he ends up having some proper HH feats, but in his run from the 70s he will also have some low end feats.
BTW I am not hating on Bendis. I like some of the stories, especially DareDevil. I just don’t like when writers misuse characters.
It is almost better to create a new character to take a fall rather than destroying something that has been built up for decades just to show how XYZ is really powerful.
For example, if there is a new villain called KillerMovies and I want to show how badass he is, what normally happens is they use an occasional guest character like Gladiator and the new villain destroys Kallark like it’s nothing. While that does show how powerful KillerMovies the villain is, it slowly erodes the value of Gladiator.
DC has also done the same with Martian Manhunter. A being that on a good day should beat Superman is often used now to show how powerful a new villain is, and overtime MM has developed a jobber aura when I personally consider him much (much!) more dangerous than most versions of (non-bloodlusted) Superman. DC has even tried doing the same with Black Adam, but fortunately not as bad as with MM.
Writers should create better ways of establishing scale, but unfortunately most will resort to using an existing character and diluting that character in the process.
That’s what happened to Gladiator.
He should be at Superman level, but he’s been disrespected in a way DC would never do for SM or Wildstorm/DC wouldn’t for Majestic (although even there DC did try to experiment a bit with Mr M when they got Wildstorm, but fortunately not too much).