Obviously a potential match up that comes to mind is against Valuev. LOL, The Big Show would outweigh him by around 100 pounds!!
"Former seven-foot professional wrestler Paul “The Big Show” Wight, who claims to have dropped down to 449 pounds from the more than 500 pounds he carried while with World Wrestling Entertainment, is supposedly training to become a pro boxer, Wight told a reporter from the Miami Herald." source
"Wight subsequently began training at the Phantom Boxing Club in Miami with the intent of becoming a professional boxer." source
"Former seven-foot professional wrestler Paul “The Big Show” Wight, who claims to have dropped down to 449 pounds from the more than 500 pounds he carried while with World Wrestling Entertainment, is supposedly training to become a pro boxer, Wight told a reporter from the Miami Herald." source
"Wight subsequently began training at the Phantom Boxing Club in Miami with the intent of becoming a professional boxer." source