Niccolo Machiavelli was an Italian political philosopher. He is famous for writing The Prince, a book written to instruct a prince on how to get ahead in the world.

He advised that the prince use any means available to take advantage of anything he could... For example, encouraging warfare between other territories so that they would be too weak to attack him, and be easier to attack if the opportunity should arise.

Anyone who manipulates or takes advantage of another can be called Machiavellian.

If this isn't strong enough, you might want the word 'Svengalian'.