who has been triple g's toughest opponent in his career so far?

I think that Stevens tagged GGG the hardest and showed his chin to be solid.

The best fighter 'on paper' was probably Murray or maybe Lemieux.

That "hardest" fight probably Ouma because it's known that GGG was not feeling great beforehand.

And a shoutout to the guy that said Khomitsky. At 7 fights that's a big step up.

Gennady has a very solid resume. He's beaten fighters who have thick resumes, convincingly. Even guys like Rubio are no joke. Maybe he has beaten no ATG calibre fighter, but the ease of his victories speaks for itself.