There are no Paladins in Shadowrun...and if there were, they wouldn't be running the Shadows.
Well, not counting the ones from the Tir, yeah.

I'm a tremendous advocate of well thought out Negative Qualities, for the simple reason that
there should be something wrong with you to take this job.
If someone was completely mentally stable, didn't have deadbeat friends he lets manipulate him, didn't have a social disorder, didn't have a tragic past that haunted him, didn't have a unique medical problem, didn't have tremendously powerful enemies that make him poisonous to be around, wasn't tangled up in organized crime, didn't claw his way from abject SINless poverty, didn't have an issue with authority figures, etc, etc, etc, and still had 400+ build points to spend on himself -- why isn't he holding down a stable, legal, regularly paying job somewhere?
Why isn't your street mage teaching at a college or working full time in Thaumaturgical research? Why isn't your combat medic riding in a DocWagon chopper or operating at a hospital? Why isn't your street samurai Adam Jensen'ing it up somewhere as the head of corporate security someplace? What reason has your hacker got for not raking in the nuyen from a cubicle somewhere, relaxing in air conditioning as he plugs his brain into a computer instead of getting shot at?
There should be something
wrong, either fundamentally, socially, or tragically, with your character for him to be running the shadows. And Negative Qualities are a terrific way to define that "something," to hash out the details with your GM, and to make sure that the game remains nominally balanced regardless of what your "something" is.