Michael in Lost. Does a lot of stuff to save his kid, a lot doesn't go his way and he gets branded a traitor for the rest of the show and condemned to Island hell while characters like Locke and Ben do unjustifiable shit often with bad moral compasses guiding them and get happy endings.
The Step dad in 2012. I haven't watched the show myself, but watched it around family watching it and he saves the heroes family and keeps them alive until the end when he gets killed off and forgotten a second later so the hero and his ex and get back together.
Can't blame Yar's lack of development on anyone but Denise Crosby, who in essence put a phaser on kill and shot the character's future because apparently she was allergic to money. Before you say recast, the series was already a big risk and recasting her may have put TNG in an early grave if they screwed it up. So instead they decided to use her as the "anyone can die, not just redshirts" example. Sucks, but that was how things worked.
Her death wasn't the problem, the episode they chose to build her death around was. It was a bad, at best mediocre ep and it dragged her death down with it.
For games, it would be Zalbaag. He's a decent guy that happens to become an antagonist and winds up fighting you in the end because of being mindfucked and given a gem to use.
Yarr stands out because it was season 1 (though she wasn't handled that great but more on that in a sec) but no one had much faith in season 1 at the time...in retrospect it wasn't the best career move on her part but how would you know that at the time? whos to say TNG wouldn't get passed 2 seasons and be known forever as a bizarre joke? (or "I don't know I kind of liked it" at best")
The only thing that saved TNG was Gene dying during season 2 and allowing sensible minds to finally save the series from his wish-fufillment obsession and finally bring drama into the series. With that in mind, I can fully understand her decision.
Who would bet their career on hoping the head of the show you're on will die before it gets cancelled? I bet at the time she thought she got lucky getting off the sinking ship so early until she found out he kicked it and suddenly the show picked up and became what everyone hoped it would become.
On top of that, IIRC she was the only one really do anything beyond Star Trek at the time being in movies here and there (She was in Pet Cemetery 2 I think) while the rest of the cast save Stewart were pretty much tied to the show.
I assume you know the technical reason to Saruman being cut like that, the length of the film, having to cut out stuff that doesn't directly affect the story, blah blah blah, but anyway. I'm gonna go and put this in a spoiler, in case someone hasn't read the books yet, and wants to do so without having their shit ruined.
Except it did directly affect the story, only it wasn't the story Jackson wanted to tell.
The Hobbits and their experiences were at the heart of LOTR and their coming home as war veterans to see the Shire had been touched by evil and that they could never truly go home again because home had changed as well was key to the themes of the story Tolkien laid out (it echoed his return to England after WWI and was a criticism of Merry Old England which sadly people still think to their day is something he praises and idealized in his books), but Jackson just wanted the shows packed with sword and sorcery because those were the parts of the book he loved the most.
On the one hand, it meant he developed a personality other than "French guy with British accent and unexplained nationalism," but on the other hand, it wasn't a really good personality.
Picard's odd national nature could have been a good moment in Star Trek for them to lamp shade how much culture and nationality had changed since our times instead of people being stuck 10 minutes into the future loving everything about history we know about and nothing that took place between them and us.
On top of that it could have been a good moment to show how much technology had messed up culture, where universal translators have become so endemic to life that humanity still speaks different languages, but it's rendered moot because the UTs made everyone understand everyone else.
Have it where Jean luc grew up around English people (which instilled in him the love of English culture he has on display during the series) and so his mind filters everything around him via the UT as being English sounding English in the same way we all read second languages through our first and "speak" in that primary language in our mind's eye.