Well Vader thought he and Luke would bump off the emperor ... Vader was getting fed up of having to listen to the emperor's irritating slow drawl, and having to check out those ridiculoulsy yellow teeth from close quarters, everytime Palpatine wanted to give him instructions.
The emperor thought he and Luke would bump off Vader .... the emperor was getting fed up of having to listen to his heavy breathing, and besides Vader was getting senile and slow in his old age. Towards the end, he tried to force choke this stormtrooper ... and ended up catching a cold in the process.
They were both wrong.
1041.