safest is primo, its non 17-a.
All 17-a kick the liver, anavar kicks it less than all the other 17-a, anavar is actually less hard on the liver than Tylenol, but some people have very sensitive livers, and cant process the 17-a as well as others.
Best bet with orals is to monitor the liver values with your doc, or graduate to injections, which is safer...