Most of us like to think that compared to kryptonians, WW is pretty much just a very fast street leveler.... Most of us think Superman wasn't bracing when WW headbutted him, or maybe that's just a PIS.
Did you notice this though?
Doomsday punched WW, she was knocked back far away....
BUT, Doomsday was also pushed back a little bit!
In my opinion, this is easily one of her best strength feat, and an undeniable one at that.