I personally think it's either has to be Miguel O'hara, or Hobie Brown (Prowler). Both of them have claws to use for climbing, and special shoes/feet to climb, both are very intelligent, both have impersonated Spider-Man, both know Spider-Man and Peter Parker, and both have less morals than Peter. I know both of them haven't been seen in a while, but maybe that's the point? It could be more shocking if it was someone we hadn't seen in a while.
What do you all think?