100% Lore abidding answer: Fuck if we know. We only got one story that relates the demon's bargaings with the gambler Tahm Kench (he takes the name of the last person he "dealt with").
Speculation: I suppose it would be possible. For example, let's say an ancient Shuriman struck a bargain with the River King to become Emperor. The first thing he does as Emperor is to decree his immediate Ancension. If not superior, an Ascended is probably at the same power level as the demon, and as such it'll probably be able to fight him off.
The River King would probably be smart enough to foresee such eventualities, making this a moot point... unless he was overtaken by hunger. He/it loses his calm and his planning skills when starved or when his meal closes, as shown by the quotes he ushers when at 3 stacks: "MEAT!" and "GIVE IT TO ME!" replace the normally composed demon's speechcraft. If one were to bargain with the River King when he had been deprived of a meal for long enough, or if one was to use the opportunity his gluttony provides once he comes to colletct to use some sort of magic, power or device that would allow to turn the tables on the demon... then perhaps one would be able to outbargain the River King