I wish he actually did give up. While he's working for his own principles and indeed trying to further punish those whose official sentence can be viewed as too light in the public opinion, at the end of the day, once he gets caught, every criminal he could have dealt with in the future will walk as a happy, free person. In the bigger picture he should understand that he needs to work for the statistics, not getting obsessed with any particular individual, especially it's not a genuinely scandalous individual. This particular scumbag did rot in jail for over a decade, so he's far from the worst imaginable case. Eventually he will also get snatched by the police for selling drugs as well.
There are far, far too many loose ends now for the MC in this case. The drug kingpin might even have his face in his database as a suspicious individual (possible undercover cop or a rival gang member).