Good question.

My gut instinct says that you can tell more about a fighter by who the lose to. But, on reflection, no one ever seems to care about who beat you, you will only get remembered for who you beat.

You can take any big name and we all gloss over the people that beat them.

Manny Pac- Rustico Torrecampo, probably owns a nacho van somewhere now, beat a legend, but no one cares and no one looks at Manny any worse because of it

Tyson
Lewis
Kilt
Ali

You could go on with any great fighter, we don't care who they lost to, it's all about who they beat.