-Dropped a building on Spider-Man
-Took out Wonderman
-Killed Gwen
-Kidnapped Aunt May twice
-Killed Ben Reilly
-Put Flash Thompson into a coma
-Corrupted his son
-Spawned the Hobgoblin and others
-Blew up the Daily Bugle
-Took over NYC's underworld in a week
-Beat Spider-Man, put him in chains, and carried his body across the underworld for all to see
-Beat Pete within an inch of his life with his bare hands, and just walked away to show him who's boss
-Has beaten Spider-Man almost more than any other villain(those two I listed, however, were the top)
-Found out Spider-Man's identity through plotting and intellect
-Crippled a random citizen just to show Peter that he's not kidding
But if you're asking how it works, GG had the equipment and journals. Kingsley found them, and became a threat. And then he wanted the journal, which increased motivation.
So it was all a basis of Norman.
Kraven, Mysterio, and The Chameleon. They're all incredibly boring characters that make no sense.
Sorry, but not amount of training in the jungle could make Kraven on par with a spider-like super-human. None of them could logically be a challenge to Spider-Man. Yes, in the comics, but the their ideas were always unplausible.