Kraven drugged Spider-Man and buried him. Then he dressed up as him and went around town beating the shyt outta bad guys so he could prove that he could do what Spider-man does...in his own twisted way. Spider-man dug himself out of the grave and found Kraven at his home where he killed himself. I forgot why he killed himself though, guess he was just fukked up in the head.
Its called Kraven's Last Hunt btw
yeah, that's all it was. Kraven had beaten Spiderman and "killed" him, then he went out and beat up some crooks, then he went out and caught c-list spidey villain Vermin on his own.... something that Spidey couldn't do and needed Captain America's help with.
He felt that since he had hunted and killed that which he felt he couldn't (Spidey was his "Ultimate Prey"), became it and did it better... that he didn't have anything left to live for.