#2 Doesn't Want Back: Paul London
Everyone knows the Vince McMahon/limousine storyline was one of the biggest thing to happen in 2007, but it did not play out correctly due to the death of Chris Benoit and his family around the same time. When the WWE boss was walking to his demise, the entire locker room was supposed to look despondent. Paul London, however, sported the biggest smile which made Vince fire him.
Post his WWE exit he has spent his life trash-talking about Vince and the company. It has not helped him in anyway, so we expect London would not be welcomed at WWE.
#1 Doesn't Want: Bret Hart
The Montreal Screwjob made Bret Hart leave the company for good but turned Vince into a villainous boss character on TV. They have buried their hatchet, but the tension between the two men will never go away. Hart is still critical about the WWE in his interviews. In fact, the Hitman has nothing positive to say about Vince and his days at the WWE.
It seems the company would not want to have him back simply for the reason he does not want to be there.