Interesting point about Sauron corrupting Ar-Pharazôn. While he was definitely imious right from the start, Ar-Pharazôn was not foolish enough to attack the Undying Lands until Sauron whispered sweet nothings into his ear. So, Ar-Pharazôn may not have been evil from the start, but he was proud, arrogant and perhaps a little naive. Prone to evil, you might say, moreso than someone like Aragorn would have been. But in this case it definitely took two to tango - Ar-Pharazôn with his position of power and his pride, and Sauron with his words and manipulations. Similar in that respect to the Théoden/Wormtongue episode, although of course the outcomes were quite different.
Regarding Gollum, I have recently been posting on
this thread, and I'm sure there are many others out there. The search engine is a wonderful thing.