Biggest Names That Conn Possibly Beats AtHeavy?

Conn would leave that guy thinking that he was shadowboxing. Tua moved slow and thought slow.

 

I do not know if he was slow witted, although Ali famously got a very low score on an IQ test & embarrassed said "I said I ws the greatest, not the smartest". But he obviously was smart in many intuitive & boxing ways.
Tua did not have slow hands.
He also was not a slug when he was helping break a record for most punches in a HW fight, & among the top in another bout.
Yet sure Conn was faster.
Louis did not have fast feet, & caught up with him despite being foolishly dehydrated.

Perhaps Conn is the minimal weight someone can be & bear up under whatever Tua manages to land.
You would cite peak Jones too, although rehydrated he was bigger.

 

I don't think Conn was clearly better than Gibbons.