Just started watching Unbelievable on Netflix, first episode but seems like it will be pretty good!!
Unbelievable is fantastic. I thought the first episode was slow and nearly gave up but Merritt Wever changed the game for me. Never seen her in anything before but she was mesmerising in this. Excellent. Should have won way more awards than it did.
Would also recommend....
The Tunnel (Sky) - first series is the British/French version of The Bridge (which I've never seen) - after that, the other two series are original stories. Stephen Dillane & Clémence Poésy are excellent together as the leads and I cared so much about Karl & Elise's friendship that it made me cry (a lot)
Cardinal - all four seasons should still be on iPlayer. Canadian take on Nordic crime thrillers. Again, I was so invested in the relationship between the two leads, played by Billy Campbell & Karina Vanasse. Actually still feel a bit bereft it's over. First season is pretty grim if you don't like watching torture (I don't)
Black Spot (Zone Blanche) - French crime/mystery series. Three series on Netflix. In fact, any French crime drama generally gets my vote.
Manhunt - one of ITV's takes on "true crime" - this one is about Levi Bellfield and was surprisingly really gripping even though I know the story. Little Boy Blue was also very good. I haven't watched A Confession or White House Farm.
When They See Us - Netflix. Not watched it myself (it's on my list) but it won a ton of awards (stole them off Chernobyl and Unbelievable) It's a drama about the real life wrongful conviction of five black youths for the assault and rape of a white female jogger in New York.
Luther - I've watched every single episode right from when it started and I've enjoyed it but it's not realistic at all. He's just another on the verge of a mental breakdown cop playing by his own rules (as they all are)
As someone else has said, the first season of True Detective is excellent. Haven't watched any of the others so can't comment but the second one was absolutely panned.