As far as I know, the safest significant city crime-wise is Nicosia, Cyprus, which typically has between zero and one murders per year.
But crime isn't a very sigificant factor in safety for most people. The things that kill people are cars and unhealthy lifestyles. Fortunately, you can avoid cars in most parts of the world and you can avoid unhealthy habits (smoking, excessive drinking, fatty and salty foods, couch potatoing) no matter where you are.
Worrying about being killed by a criminal when you choose to live somewhere that requires you to drive to work each day is statistically foolish, because the car is vastly more likely to kill you.
So, pick somewhere that's not a war zone, live where you can walk or ride the subway to work, get frequent exercise, stop smoking, drink in moderation only, and lay off the chips, and you'll find yourself safer than the vast majority of your fellow humans.