Julian Jackson -Could he defeat any of the Famous 4?

Hes nominally capable of beating all of them. He'd probably beat Duran he'd probably lose to the others.

The big 4 as a group are overrated if you take them as equals to Mike McCallum H2H.

 

Some need to quit acting like Hagler is Super-man, he wasn't and anyone can be knocked out against a puncher like Jackson, Hagler was rocked badly against Hearns in the first round before Hearns broke his hand.

 

Outside of a puncher’s chance, probably not.

 

What Hearns did to Duran, Jackson most likely would too. Unless it somehow went the distance, and maybe Duran might win a decision. Possible but not likely.
Leonard doesn't have the power to match Jackson, and is severely outgunned and outmatched.
Hearns, with his range and right hand, could end it quickly, unless Julian catches his chin, a la Terry Norris and Herol Graham.
If the Hawk catches Hagler cleanly with some bombs, that could make things interesting. But most likely, the iron headed Hagler dispatches Julian in the manner of Hearns and Sibson.