I don't mind the violence, the nastiness, the seedy druggy underworld, hey, I grew up in Sarf Lunnun, what I object to is the manipulativeness, you could plot a graph on Walt's rises and falls, he makes money, he has to lose money (because meth is BAD). Up and down, throughout the series.
I also find Walt utterly unbelievable and his character development frankly ridiculous. I have known plenty of people who work on the less conventional side, and they do what they have to do, but they remain essentially themselves. Walt, a loving family man, turns into a raving loon who bullies and abuses Skyler, the Cipher Wife.
Marie is just ditzy (at least she wasn't blonde) and never seems to go to her nurse job, and imagine trusting her with a syringe, Hank is a walking stereotype.
I did like Gus, but it was intensely annoying not to find out about his past in Chile (and lazy of the writers)