Ideally, all of our TV heroes would get the happy ending they deserve. They'd save the day, have the successful romantic relationship, and get to live a life with a bit of peace.
In fiction, as in reality, it's never quite that simple. A lot of the time, being a hero means you end up sacrificing your life. It's not all bad, because this can at least result in some extremely satisfying storytelling and character work: from Ned Stark in Game of Thrones, to protagonists who were more anti-heroes in the end like Walter White, there's something painful yet brave in killing off the lead of a show.
It doesn't necessarily feel 'good', but that's all part of the TV experience and what makes the medium such a powerful tool for telling stories, because it means we've invested a lot of time in a character or plot. Sometimes, though, endings for characters aren't quite so clear. Sometimes the future for the hero - or heroes - is looking a little murkier, and what may seem like a sense of closure and even an actual happy ending is instead most likely to lead to their death, and not of the 'quietly dying of old age' variety.