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Lots of different sources and interpretations on Boba and his personal outlook on the galaxy and Good or Evil alignment. There are lots of expanded universe stories in comics, novels, and stories, though that's not always a help since they can often conflict depending on the outlook of each author. This is probably the key factor behind Boba's popularity: the mystery surrounding his outlook and motivation.
Personally, seeing him in the movies and knowing some of his EU stories, it's difficult to know fore sure if he was truly dark or just the hunter doing a job. Nearly all his bounties in the EU are in fact rouge Imperials and actual criminals, all villains and worthy of whatever fate Boba’s clients gave. To my personal knowledge, which is I admit limited on the subject to be honest, Boba never took a bounty where the target was an entirely innocent and righteous person. One could argue that point based on the movies, however, keep in mind: in Episode V, yes Solo is a hero to the Rebels and at heart a good man, but by all rights he was a criminal before and after he joined the Alliance. Not to mention he had foiled Fett on a number of occasions in the past, making Boba that much more eager to even the score. By Episode VI, Fett was soaking up the glory of having cashed in one of his most lucrative scores, and Jabba was always a source of new contracts. Despite the obvious evil company he keeps, Boba always seemed to maintain an aloof manner to his employers; the contracts were just bounties to be taken, not personal missions for a cause or (with a probable exception to Solo and maybe to Jedi as a whole) personal scores.
Another argument for Boba being evil would be his hunting of Luke in the Holliday Special and in other accounts. Luke was a simple farmhand until the war, and his only crimes were against the Empire, which in and of itself is evil. Therefore, why would Boba take up the contract if he himself wasn’t evil. Of course, there is now the point that Jedi killed his father, and the personal score many like to read into that. However, I give Boba more credit as an intelligent being not to hold an entire order to blame for his father’s death, especially twenty years later. Therefore, this is where I like to read into Boba’s character a Mandalorian heritage taught to him by Jango and further developed later in life. He hunts bounties to test and hone his skills, he fought Luke because he was Jedi and therefore a honored foe and challenging adversary. It’s all a pattern that could be explained by a man following the ancient Mandalorian warrior code.
There are tons of other theories and lots of conflicted sources to absorb inspiration from. At the rate contradictory expanded universe stories and cartoons are being authorized and churned out any real answer will be even more impossible. Just more reasons to imagine in your own mind who and what the perfect Boba really is, and don’t worry about what’s cannon today or what will be tomorrow. That’s what I do.
"You set a code to live by. I won't be wronged, I won't be insulted...I won't be laid a hand on. I don't do these things to other men, and I require the same from them."