I'd say the "strongest version" of Parasite was the DCAU version after he absorbed Mxy's power/experience. And in that case, he should win...
Parasite: "The universe is putty in the hands of a high school dropout, thanks to you, little man!":
https://i.imgur.com/Pmhxjw4.jpg
Superman: "With your [powers] he could de-create the universe!":
https://i.imgur.com/hJ9iPJd.jpg
Parasite: "I've got your experience, Mxy, remember? I stole that, too... And with my experienced five-dimensional mind, time and space are just building blocks, to be arranged in any way that makes me happy.":
https://i.imgur.com/g8ncFyi.jpg
Parasite: "With powers like these, Mxy, you could've reassembled every atom in the universe, from the big bang to the end of time!":
https://i.imgur.com/TCb8IBH.jpg
Parasite then used Mxy's power to warp the entire 3rd dimension in his own image...
Mxy: "My guess is that he used my powers to give the third dimension a fresh lick of paint."
Parasite: "Not just a paint job, squirt -- I've rebuilt everything to be a little more Parasite-friendly.":
https://i.imgur.com/JTw2sRZ.jpg
Originally posted by abhilegend👆
And that is canon to comic mxy too.👆
First established in World's Funnest:
https://i.imgur.com/chcbyDC.jpg
https://i.imgur.com/EQg4Sqm.jpg
Then corroborated in Action Comics #975:
https://i.imgur.com/WSpOlCI.jpg