Actually Grayson as NightWing is a pretty hard hitter...certainly not driven by exactly the same motives at first but later learning that his parents hi-wire death was no accident (in the comics)...add to this that his relationship with Bruce ended on hard terms and since taking on his own persona of Nightwing has been constantly trying to prove to "the old man" that he has the goods to stand on his own.

This was one of the reasons I enjoyed "Batman Beyond" so much. Terry McGinnis was as driven as they come and bitter over the loss of his father and the fact that he never made peace with him...ad to that his brash and cocky youth streak and it made for pretty entertaining witty dialogue. Of course with still having an aged Bruce Wayne as a mentor and teacher but creative writers can find ways to fill those voids.

This is the huge benefit that the comics genre has at their disposal. They can kill off characters or alter their story line and then guage public reaction (look at how many times they have screwed around with Superman)...its great way to feel story lines out before they move farther up the "development ladder"