near as I can tell, short of keeping hens in a concrete bunker, nothing is predator proof! I do have a few huge pines in the chicken run which provide cover, as does their coop, which is an old construction office trailer painted barn red, leaving them lots of space underneath for shelter and dustbathing. I have a 5 foot fence with an electric fence wire, and 4 feet of wire fencing laid on the ground flat surrounding the fence, which is wired to the upright fence. Added the last part (wirefencing laid on the ground) after a power outage left the electric fence useless, and a dog dug under the fence and slaughtered the flock.
I'm sure I will still lose some chickens to other predators - I'm worried about weasels and minks that can slip through the wire fence and miss the electric fence, which is currently useless as it is buried in snow.