Consider that Finn has all the hallmarks of a typical action hero. Compare him to Jason Bourne:
Both are highly trained and skilled soldiers defecting from an overreaching government with unfathomable resources and sociopathy
Both are the "top of their class":
[TFA prequel] At last she said, "FN-2187, your targeting was exemplary. According to the simulation, you fired your weapon only thirty-six times, scoring kills with thirty-five of those. You deployed one explosive, which resulted in the achieving of the objective and another six enemies killed."
[The Bourne Identity] I can tell you the license plate numbers of all six cars outside. I can tell you that our waitress is left-handed and the guy sitting up at the counter weighs two hundred fifteen pounds and knows how to handle himself. I know the best place to look for a gun is the cab or the gray truck outside, and at this altitude, I can run flat out for a half mile before my hands start shaking. Now why would I know that? How can I know that and not know who I am?
Both are forced to engage in combat with their "brethren". Both, despite having a rule against harming innocent people, are willing to kill operatives of their previous allegiance ruthlessly and efficiently
It can be argued that the other operatives in Treadstone are not Bourne's "brethren" because they work alone; however, it's obvious from The Bourne Supremacy that they know each other and are capable of empathy/camaraderie to an extent
Both are highly valuable assets:
[TFA prequel] She sighed. She’d had such hope for FN-2187. He had shown such remarkable promise. He had shown the capacity to be special.
[The Bourne Identity] You're U.S. Government property. You're a malfunctioning $30 million weapon. You're a total goddamn catastrophe, and by God, if it kills me, you're going to tell me how this happened.
Both are "haunted" by their job:
Finn doesn't want to execute innocent people.
Bourne feels guilty about a job in Berlin.
I could go on but I believe I've made enough examples. Like Finn, Bourne was conditioned to be a killer. Most of Bourne's journey is rejecting this conditioning and going after the source of his training. In the process, Bourne stuggles with his "dark side", aka the blood on his hands. However, speculation strongly suggests that since Rey is the heroine of the film, then it's possible that Rey is more ala Luke and will be tempted to the dark side. Of course, Finn's character alone is a change from the formula and there's nothing to say that the writers won't try to (predictably) alter the formula by having Finn turn to the dark side instead.
So my question is, is there any evidence that Finn is capable to turning to the dark side, to make this a plausible potential plot point in a future film?