What type of things would constitute my my wife who is divorcing me as an unfit parent?

What type of things does she do that you feel are unfit?
Neglecting the kids?
Is she getting drunk/doing drugs/partying/bar hopping?
Does she make sure they are taken care of?
Feed/clothed/school on time?

Or is she claiming you as unfit and why?

You'd have to substantiate actions on her part that clearly endanger the child's physical and/or emotional well-being. An attorney can give you some guidance. Also if you want to provide us with some specific examples, meaning what kinds of things does your soon-to-be ex-wife do that you believe make her an unfit parent, we could maybe give you an educated guess as to whether a court would find her unfit.

What state? You may enjoy some reading: Custody.com