A few people have named Braddock. My response would be that Braddock was an inconsistent quantity. He lost to somewhat worse mean than Cooper, and he beat somewhat better men!
WBA holder, Ellis with clear wins over Martin, Bonavene, Quarry and lasting 15 rounds with Patterson, would more than likely stop Cooper.
Probably not many. There are several who he’d give a good fight to though. Cooper was a game opponent
I don’t think there are any that Henry outright deserves to be favoured over. But that is no disgrace. There are a lot of memorable challengers who came close to beat great champions who also don’t win a linear title because they don’t deserve to be favoured over a linear champion. Even guys like Arturo Godoy, Jimmy Young, Bill Brennan, Ron Lyle, Billy Conn, George Chuvalo and Oscar Bonavena. Even guys like Tommy Morrison, Tony Tubbs, Ken Norton and mike Dokes who never qualified as real champions!