Mr Satan tries to convince your favourite character to let him win the World Martial Arts Tournament.

[The_Wright_Way]

I mean, Cole has already kinda been covered, so I'll go with someone else.

Karkat Vantas: This admittedly kinda depends on the extent of his prior knowledge. Like, if Karkat got to know Hercule beforehand, then he'd probably throw it after deciding he's not that bad of a guy. (Albiet, he'd do it in a "I'm not doing this for you" kinda way). With the knowledge given, however, I'd say no. Karkat would actually be kinda insulted that Hercule is a fraud. In fact, Karkat's Social Influencing is good enough where I can actually see him turning this around on the champ and getting him to fess up. Not to knock the champ, but Karkat is a force of personality that he just can't compete with. As soon as he spits out the offer, Karkat is going to toss a certifiable thesis at his ass.

Rose Quartz: She blinks, gives a bemused laugh, and then just rolls with it for kicks.

 

[Stillwinston]

Alucard (Castlevania) - I can see him being convinced, that or just views it as waste of time.

The Highwayman (Darkest Dungeon) - Probably blackmails Satan for cash, could be convinced though.

Kazuma Kiryu - Errrr yeah he would I think, probably disappointed in Satan but he'll let him win.

The Ancestor (Darkest Dungeon) - Yeee nope, Satan gets flayed or sees things and goes insane

 

[DaReaperMan]

Overpowered necromantic powers, go!

Hercule: (insert convincing here)

Oryx the Mad God: "Your champion is weak and a fool! I will trample you underfoot!"

 

[The_man_with_the_Midas_touch]

Usopp: I can see Mr. Satan convincing Usopp to let him win. Usopp is fine with tricking and lying to people, so he would have no issue with fooling the audience.

Mako Mankanshoku: I think Mako is nice enough to let him win honestly.

Lupin III: Lupin strikes up the same deal that Hercule made with 18. So he loses, but Hercule pays him a hefty amount afterward. Knowing Lupin, he probably only joined the tournament to steal something and isn't actually interested in being a martial arts champion.