“Note that Grundy’s strength and tactical prowess vary with each resurrection, though.”
Thank you, N8.
Grundy’s resurrection just before Blackest Night had him up against big guns like Bizarro and Etrigan. (Croc as well, but he was Worfed big time, as usual. He put up more of a fight within Bane.) His resurrection at the end of New Earth had him mastermind his own permanent immortality. Even in his earliest appearances he could be a whole League problem, other times he’s simply been electrocuted to [un]death.
Any writer could have Grundy resurrect to be smarter and stronger than Bane. Someone could even have Venom tanks dumped in Slaughter Swamp to create Venom Grundy.