Consider the under-cover Good cop.
Right from the start, you complicate this discussion by making good synonymous with 'law enforcement' and later evil synonymous with 'criminality'.
I don't know if that is because of your bias or if you are just doing some handwaving here, but by know means must we assume 'police officer' implies 'good' or that his motivation to not break laws has anything to do with his goodness or his desire to promote goodness. The 'police officer' may believe 'law = good' (in the sense of right and proper behavior), just as in my prior example the champion of evil believed 'evil = good', but even that cannot be taken for granted.
So, we must pare down your example to its heart which is, "Consider the good person who is practicing deception in order to achieve ultimately some good end." To begin with, we might want to ask whether a good person is going to be doing this at all (Boy Scouts don't make good spies), deception not being a regular part of the tool set of good.
But, even if we assume this, I don't see how it follows that because the Evil person doesn't have the the same qualms as the good person, that they don't have qualms. The question you have to ask of people engaging in evil behavior is, "How easy is it for them to stop doing what they do, even when they know that stopping the behavior is in their best interest?" And I think the answer is pretty consistantly across the board, "They don't find it easy at all." In fact, they find it probably harder to stop being evil and do something good - even when they know that it would be in their interest to do so - than good people find it to stop doing good when they think it is in there interest. Someone said, "Good is hard. Evil is easy." And, that's true, but it cuts both ways. Stopping being evil is hard. When the evil person wants to stop their pattern of behavior, they find that they have serious 'qualms' indeed that push them to continue with at least as much force as the revulsion a good person feels when they are forced (or believe that they are forced) to do something evil.
In practice, we don't find that people who are evil really exhibit the sort of freedom of choice that gamers like to attribute to them. This is because evil does instill 'qualms' - a strong revulsion against performing some sort of behavior - in those that practice it.
An under-cover Evil person doesn't have those qualms. He's doing good things (or not doing bad things in public) to blend in.
That's not how evil tends to work. As Spock says to Kirk, "It was far easier for you as civilized men to behave like barbarians than it was for them as barbarians to behave like civilized men."
At most, he's not happy being constrained...
At most??? At most?? He's
not happy??? No, he's furious, and he's a person who is used to endulging his fury and who sincerely believes it is his right to do so. His inner being cries out for proper release. He has to supress (perhaps quite literally) a raging demon that is outraged that he's born insults against him, that's he's coddled the weak, and that he's acted fearfully in the presence of his enemies and humbly in the presense of his inferiors.
Bad guys commit crimes because they think they can get away with it.
Bad guys aren't criminals necessarily, and conversely criminals aren't necessarily bad guys. Neutrals commit crimes 'because they think that they can get away with it'. Bad guys commit crimes because they think that their victims deserve it, and because they think that they have the right to do so and they commit 'crimes' even when they can't get away with it because that's what they believe they must do. In fact, they often don't want to 'get away with it', they want to flaunt what they have done publicly to show everyone what happens when they are crossed and to preach how deserving their victim was.
They're not agents in some black vs. white war of wills.
How do you know?
Mostly they are self-centered...
Self-centered is Chaotic, not evil. Many sociopaths aren't self-centered at all, and not all criminals are sociopathic.
Evil does not have principles. Out of all possible actions, it will choose any of them that suits it.
Of course evil has principles - evil ones. Not having principles and not taking a stand on your principles is neutral.
Evil seldom has regrets, mostly being limited to tactical mistakes (I should have shot the guy on the left first, I'd have taken less damage).
What the hell is vengeance if not motivated by a regret? Evil doesn't 'sorry', but that doesn't mean that it lacks regrets. Evil is often consumed by regret, it's just not motivated to act in the way good is motivated to act when it feels regret.
