What turned me off about the Sopranos initially was how sociopathic, damaged, and unlikable the cast of characters were. On second viewing, I realized this aspect is what made this show so brilliant in the first place.
Most crime fiction has the trope of the sympathetic criminal. The characters lead a life of crime out of necessity, and have at least one admirable trait that makes you want to root for them, like having a strict moral code or being a loving family man. To paraphrase Wreck-It Ralph, they might be bad guys, but they're not "bad"
However, some works of fiction such as Goodfellas and The Sopranos take a decidedly more honest approach. Nearly all the mobsters on the show exhibit violent, anti social tendencies. While they might talk about family values and mafia code, there is no honor to be found.
The other civilian characters aren't that much better. Dr. Melfi is too enamored with Tony to drop him as a client, and her therapy indirectly validates his actions. Artie is a coward who creeps on his female employees. The FBI are portrayed as incompetent and indifferent to the lives they destroy in attempting to catch criminals. Janice is a machiavel who let her son become homeless. Meadow is a spoiled narcissist who grandstands about social issues, yet is very willing to play the role of the mob boss's daughter. AJ is a frat boy with no moral compass.
No one is born evil and the show explores how nearly everyone became who they are, but this doesn't negate their actions.
The most moral of the main cast are Adriana La Cerva, who is a legitimately kind person who might not entirely be to blame for covering up crimes, Jennifer Melfi who tries to help Tony, but her relationship with him is mainly just a voyeuristic fascination, and Carmella Soprano who is a great mother to her children, but also greatly benefits off of the misfortunes of others caused by Tony's criminal activities.
These might be the characters with the least negative attributes, but does their associations with criminals make them bad people?