Unless you go really high-end with Stranger, then Maaldor wins.
He treated pre-crisis Superman and Power Girl like they were absolutely nothing, and was only 'beaten' by a plot-device of his own creating:
https://i.imgur.com/W9sh1VN.jpg
https://i.imgur.com/KXSFaJl.jpg
https://i.imgur.com/pllp8EO.jpg
https://i.imgur.com/z1UfFY2.jpg
https://i.imgur.com/r8dxkpE.jpg
Worth noting that when fully unleashed, Maaldor's power was capable of collapsing the entire pre-crisis multiverse:
https://i.imgur.com/DfDmDvk.jpg
