Rules:
-Win by death or knockout
-No prep
-Morals on
-Post Crisis Jimmy Olsen
-Standard 616 Butterball
=-=-=-=-=
Fight takes place inside the Baxter Building.
=-=-=-=-=
Who wins?
Most of the time, Jimmy just loses. Or if it's the time when he was Mr. Action or one of his silver aged powered identities like Turtle Man, stalemate.
If this is the adult version of Olsen, Jimmy wins.
He'd simply strip Butterball of his pants and tie him to the nearest chair.
Butterball lacks appreciable physical strength despite his invulnerability;
Jimmy could more or less have his way with Butterball by simply forcing the fight to a grappling match and overpowering Butterball.
The late teen version of Jimmy can do the same, just not with the same ease.
Believe it or not, Jimmy Olsen has a TON of combat feats, though most are against fairly ordinary thugs. The Superman Family books are full of his heroics.
he can suffocate him. Butterball can still get tired and is shown on panel to pant for air due to his poor physical condition. So all Olsen needs is a plastic bag.