Corporations definitely exercise their ability to invade our privacy much more frequently and flagrantly, but I wouldn't say that that makes them the worst.
Governments have direct control over things like armies, cops, secret police - you know, guys with guns. This means that although the instances of privacy violation are less widespread, their implications are more severe.
Google's not going to invite some men in black to your apartment at 3am for an interrogation session, but if you mention in an email that you wish the president would die, the government just might.