This doesn't look good for the Devil, but let's analyse!
In AP, I see this as Guts having the advantage. I don't know the specific output in joules of either of them, and from eyesight alone I'd say that the Devil had more impressive feats... However, Guts wields the Dragonslayer, and as a bladed and exceptional weapon, Guts can focus the energy of his blows on a much smaller contact area, thus resulting on a much more powerful strike, all in all. In LS, I'm confused by the Devil's Class K and Guts' Superhuman. The Devil should be lower, Guts should be greater (Class 1 is a very bare minimum, and I see him as being a very likely Class 5 or maybe 10), but assuming the profiles are correct, the Devil would EASILY submit Guts, and considering his base higher AP, that would be lethal. Thankfully, he doesn't seem to use grappling/restricting moves all that much in a fight.
Guts is way more mobile and agile, and he seems to be way more experienced and skilled than Satan, and he's also smaller. He'll have a easier time dodging his attacks than vice-vicersa.
In general capabilities, I'll already start that Guts is worlds above Satan in combat and tactical skill, and arguably in smarts as well, even if the Devil isn't dumb at all and being quite devious and cunning actually. Guts' mentality and experience are far above the Devil's too, and he'd persist where the Devil wouldn't. All his capabilities complement his astonishing skills, allowing him to easily dodge and maneuver around the Devil. The Devil has more offensive options on his side, with the danmaku, energy and diverse ways of fighting. It'd be the first test for Guts, and actually a good example of what Apostles can do. However, nothing there really seems that would keep Guts at bay, since the Devil tends to stay put during fights and mostly tank attacks while bombarding the enemy with his own.
I think Guts should take this with medium difficulty, honestly. There are very few, if any, scenarios I can see the Devil pulling this off.
