If we’re talking mmath, Charles clearly beats Gaethje in the deserve category. He’s beaten him in a single round, Charles has held the title and also defended it, even beating Dustin who had a win over Gaethje at the time.
If we’re talking styles, then it’s a more intriguing argument for just Gaethje, since Islam hasn’t fought him yet.
And there’s no reason to assume khabib would beat the shit out of Charles. Khabib struggled to deal with Alquinta, and he also took longer to finish the same opponents Charles did in title fights. Oliveira can absolutely have beaten khabib, even if khabib is the more accomplished lightweight overall.
For real though, it’s too bad we didn’t ever get khabib vs Charles. Would have been pretty epic.