The Walking Dead. The first episode was the best part of the show by far, so...That was the missed opportunity. The show would've been about a thousand times better if it had just been about Rick, the crazy sheriff traveling the country, searching for his family. (Who is obviously dead, but he's in denial and like I said, a bit crazy) He could meet different people over time, but eventually he'd always end up on his own again.
Yeah, I know that doesn't happen in the comics. Well, so what? The show already diverges from the source material anyway. Might as well do it in a way that makes it better instead of worse.