I was very impressed by Task. I think it's my #1 due to the depth of the story and complexity of the characters. I was glued to the screen.
All Her Fault was a lot of fun even though it was rather shlocky. But I love shlocky stuff and this had some surprising twists and turns.
I suppose Adolescence would be my third recommendation. Not sure I'll ever watch it again, but it was very gripping.