Unearthed quest.

Killed first time, cause he stole mah money, turned into Blades other times, because I usually stop at that quest

Depends entirely on what sort of character I'm playing. Good and neutral characters let him live whereas the evil types finish him off for wasting their time.

What about righteous punishment?

I've done some research and Ralis still calls Ahzidal his lord if you decide to kill him.

And funnily enough, I tend to spare him with my evil characters because the dialogue option implies that s/he cares about the people Ralis killed.

Always let him live, saw no reason to kill him.