I know you all want to say Electronic Arts or Activision, but what I'm talking about here are the companies that develop the games not publish them.
If I had a game developer I hated, it would be Midway.
They were good when it came to arcade games and such back before the 2000's. But they went on a downward spiral with some of their games for the consoles such as Spy Hunter: Nowhere to Run and Blacksite: Area 51. I'd sure miss them if it weren't for those games.
Anyways, what would be your least favourite game developer (or game maker)?