Who is the best 0 defense Champion ever?

None of these

Young Corbett III, (123-12-20 33 KOs) beat Billy Conn, Mickey Walker, Ceferino Garcia, Jackie Fields, Gus Lesvenich and Fred Apostoli. Beat Fields for the Welterweight title then was KOd in 1 three months later by Jimmy McLarnin to lose the title. Never defended.

Corbett III is in the hall of fame, none of these choices are making it there.

 

Not Jacobs he is huge for a middleweight, and he has a 73.5 inch reach while Mugabi had a 74 inch reach and Hagler had a 75 inch reach, while GGG only has a 70 inch reach which is why I feel his jab would be less effective v Hagler and that Marvin would out-jab GGG.

 

Draws are considered to be successful title defenses, so Jojo would be excluded from the list.

Anyway, my personal answer is Jimmy McLarnin.

 

You beat me to it. McLarnin regained the belt by defeating an ATG Ross after dropping the belt in their first fight, but lost it again without a defense in the rubber match.

 

Ken Norton deserves a mention.