Only ppl to decisively beat Tua in his peak years were Byrd & Lewis (Parker is decent but they were special..) the Ike fight was close .. Tua was pretty unique, a short but a granite chinned ATG puncher type with stamina & who could produce a high output too .. more time goes by the more I appreciate what a specimen Tua was.. he'd get to Parker.. his KO ratio in his prime was insane and it was against good opposition too.. He was dwarfed by Lewis but he kept him honest throughout that fight.. Tua was legit, could box too..
You can't compare Parker to Byrd.. Byrd was slicker than molasses, a skilful southpaw.. a great defensive fighter