I loved Dexter all the way until the end. The ending they chose sucked, but it didn't really ruin the show. You're missing out on great characters if you don't watch it all the way through. I'm currently watching Nurse Jackie and it's good, but that is a comedy. Sons of Anarchy is a must watch for you; I loved it. I'll check my netflix list and see what else I've watched. Prison Break is great. Not really dark, but it is a drama. Also The Blacklist is amazing!!!! You should also try Criminal Minds. That's one of my favorite shows. Bates Motel is also great. There's also a new show on TNT (i believe) that just started a few weeks ago called Animal Kingdom. It's pretty dark and one of my favorite new shows. I would recommend Legends because season 1 was so great, but season 2 had me so confused and really disliking it because they went a completely different way than they were with season 1. And that's all I see on my netflix list.