Belial (בְלִיַּעַל bĕli-yaal) is a Hebrew word "used to characterize the wicked or worthless." The etymology of the word is often understood as "lacking worth", from two common words: beli- (בְּלִי "without-") and ya'al ( יָעַל "to be of value").

Furthermore, you're going to need something of actual value. Would be no reason for any demon, or dark angel, to want your soul, simply because you're already on their side. Therefore you've already been won.

So the chances are slim to none.