Brolly. Interesting question. I would ask that you clarify which GR you are thinking of. I have said that in GR # 11 Johnny B. took out the Hulk by burning away the oxygen around him so he passed out. Juggy though? One of my favorite comics is where Spiderman tricks Juggs into the foundation of a building and he sinks. He kept going and emerged on the east side some time later.
Having said that, the question would be if the Gem would protect Juggs from the Penance Stare of Ketch, or the Chain or hellfire? GR could take the punishment and survive. Thinking outloud but I would say GR Ketch or Johnny B would use the chain to get the lid off, then choke Juggernaut out. Juggs could beat on him all night and GR would get up again. Does that help? Kind of longish but wanted to provide some background reasoning rather than a fanboy -- GR all the way dude
like you know! Righteous!
etc.