He should have done the very thing he said he wouldn't, and let it be a mystery. Have Pete track down kingsley, and discover that he in fact did not come back. Have it revealed in six months that it was Phil Urich who had gone insane for some reason. That would have been better than this drech.
And for the record, mysteries suck when you know the answer. Having the reader know the outcome, while the main character doesn't it so stupid and boring. And Phil Urich, while not the best character ever, is slightly likeable. Having him become some crazy murderer ruins that, he's just some crazy sociopath now, another electro. All the paths he could have went with the concept, and he just decided to go "I'm evil.... just because". Instead he could have had a guy who desperatly wanted to do the right thing, but his own mental illness was taking him to the point where he couldn't see the line anymore. You have a potentially tragic character, who is now just some evil schlubb for Pete to take down some more *yawn*. Oh and bringing back the Kingpin to Spidey's rogues? Lame, Spidey used him up and spat him out for Daredevil, no reason to bring him back. Especially after the events of back in black.
And this is the problem I have with all of this. I'm not going to lie and say I'm some big Roderick Kingsley fan (because I'm not), but I didn't like that he died like a bitch for no apparent reason, but to establish another Villain, who's just another "mustache twirler" that has become far too prevalent at the Distinguished Competition. With the storytelling techniques at Dan Slott's proposal there is no justification for him to aim at the Lowest Common Denominator like he's aiming at.
If I had to put my finger on it, Dan Slott really doesn't do his due diligence on characters that he doesn't know, which leads to situations like this, and the one where he had Quicksilver lie to the Inhuman Court in Mighty Avengers. (which caused me to drop that book) He also has a case of passing off tired concepts as new. I'm pretty sure an evil Peter Parker storyline has been done before, and is just boring with the story structure that's already established.
It's stuff like this that makes me wish he would go to DC, where he would become an instantly utilized writer with the style Didio likes to see.