This is really interesting. I think you're right about 1, 2, and 4, and yet I wouldn't give up season 2 of VMars (I'd give up the rest) or much of Musketeers or BH after season 1. It's complicated!

Totally agreed about Broadchurch, though!

For me, the answer is Killing Eve. I didn't watch after the first season, and I don't feel the need to. The first season just worked perfectly well.