Do you mean super lightweight? I know he was never a super welter weight. When Kostya Tszyu fought Hurtado, he weighed in at 139 lbs and rehydrated to 157 lbs on fight night. Tszyu was a career super lightweight. And he was in his prime when he fought Hurtado. When Floyd fought Judah, he weighed in at 146 lbs (exact same weight on fight night). This was in 2006. When Floyd fought Ortiz in 2011, he weighed 150 lbs on fight night (Ortiz weighed 164). Floyd wasn't even a big super lightweight tbf. Guys like Hatton, Tszyu, Cotto, Garcia, Maidana used to weigh over 150 on fight night when they were fighting at 140. Floyd weighed that much as a welterweight. That's the only difference. The weight class they fought at.
The red aussie could punch with a right like a shotgun and was tough as old boots! prime for prime Kostya's chin despite his stalker style carries him through a loss in the form of MD Kostya was P4P possibly the most athletic boxer ever the Soviets don't become fit doing a sport they become fit for the sport he's been sweating even before he stood in a boxing gymnasium to survive since he was a child. He's got chin, power and speed with an almost unshakeable professional attack but what separates Floyd from the animals like Kostya is an almost unrivaled ring IQ it's a fight for six for Tszyu but afterwards Tszyu is walking into punches all night with only heart left throwing the right with bad intentions possible he drops Floyd but it wont matter by six even rounds Floyd has him.