Well they attacked kakashi's squad for no reason, or at least we're
lead to believe...other then having a hit on the bridge builder. And
if you think about in this world paid assassin's are "bad" people or
vilains. so ha!
He also helped a child out of poverty. Is he still "bad?"
How about the fact that his village made him into the shinobi he is/was?
Does that make him bad?
No, it doesn't, Good/Hero/Bad/Villain are all terms used from a point of perspective. Evil to Konoha is a Sound Village Hero.
Look at it this way, a drug dealer who deals drugs for the intent of getting money to start up a drug-help corporation, good or evil?
Who knows the true intent Zabuza? He could have been trying to gather Ryo to start up his own village reformed so that there wouldn't be anymore initiations by killing their comrades? Would he still be "evil?"
Even Konoha has missions with the strict intent on Assassination, does that make the person who did it "Evil?"