Ending any script is hard. You don't want to go with the expected and bore your audience. But you don't want to go so wild and crazy that people are left thinking, "What the fuck did I just read?"
You want to hit that sweet spot right in the middle - unexpected, in keeping with the story, and leaves the reader mulling the themes of your story.
But TV pilots are a whole other animal. Because, technically, you're not finishing the story. You're just setting it up.
At the same time, you still want your reader to feel satisfied that they've gotten a full story.
How the hell do you do that?
By keeping in mind that you must "end" the smaller story and "begin" the larger story.
Let me explain...
Why A TV Pilot Ending Is So Important
Execs, agents, and even other writers are busy. They don't have time to read through every single script that comes their way. But what they will do is skim.
They'll get the gist of the story when it starts, and then they'll skip to the end. And that ending better deliver.
But more important than accounting for readers who don't like to read is the fact that, even though you have a full TV series concocted in your head, this TV pilot is all anyone reading it is going to see.
Therefore, you cannot expect them to know that you have some amazing characters and plot twists saved for mid-season. They need to be entertained now in episode one.
That's why you're really writing two stories - the smaller story and the larger story.
Ending The Smaller Story
Each episode of a TV show is telling a mini-story within the arc of the season. And that's true for your TV pilot as well.
This is the story that is going to provide a feeling of closure and "complete-ness" (that's not a word) to the reader. So, it has to pack a punch.
Let's take a look at how Futurama does this in its pilot episode (which, by the way, is fantastic, and you can learn a lot from it!)
Fry is a delivery boy in the year 1999. He hates his job, his girlfriend's cheating on him. He is a loser who has no one and wants a better job. He accidentally freezes himself and winds up in the year 2999. He ends up finding his descendent, who runs a shipping company. He's given the job of delivery boy, but he's happy because he's found community.
This is an ironic ending, of course, but also a cathartic one that brings closure to the story's episode of Fry being unhappy with his current life.
Beginning The Larger Story
Now, even though you're completing the smaller story, your TV series story cannot feel complete. The reader needs to be able to see where this story can go. They need to be able to imagine what future stories/episodes might be.
Therefore, while you're giving this cathartic bit of closure, you're opening up the world of possibilities that your pilot episode has set up.
So, in Breaking Bad, Walt has cooked some meth and evaded the cops. And now we're set off on the series, in which Walt's gotten a taste for being "bad" and he's going to take it much further.