Kingpin's rights are owned by SONY right now since he is considered a Spider-Man villain. Not exactly sure how THAT works.
This is b.s. The Spectacular Spider-man cartoon couldn't use Kingpin because Sony did not have the rights to Kingpin. That's why you had all that Big man stuff that turned out to be Tombstone.
Spectacular Spider-man was the last cartoon done before Marvel got back it's television rights; that cartoon lays out just what Sony does have the rights to. Sony does not have the rights to Kingpin.