One is an eldritch horror from the deep and the other is just an angel with daddy issues.
SpongeBob would win without even trying.
SpongeBob seems to have a good relationship with his dad, that probably gives him an edge
SpongeBob wouldn’t even realize that they’re fighting.
Satan’s chief ability is temptation but the worst he could tempt SpongeBob to do is steal a balloon on free balloon day.
Send in this one and it’s GG (for Goofy Goober)
Spongebob HAS shown an immunity to all damage provided he’s got moisture
If it’s in the ocean, Spongebob (eventually) wins via attrition
If it’s in hell, Satan wins without even trying
Counterpoint: human sinners’ sweat and tears make hell so humid that SpongeBob doesn’t feel a thing.
The one sponge to rule them all