Hmm. I'm thinking it's Bucky too who'll be somewhat the Sharon Carter of MCU when it comes to Civil War's ending but if that's the case, do you think they're still setting him up for a redemption arc? Because I cannot see any scenario where Bucky kills Tony or any of the Avengers and can still find redemption unless he's somehow under brainwashing again like Sharon was. The audience would hate him, especially if he kills the more popular ones like Iron Man or Cap, but hell, even Rhodey (nooo!).
Yeah, I think (hope?) they are still setting up a redemption arc. The Russos said several times over that Bucky is a big emotional part of the story, and if you’re a Bucky fan you’re going to love Civil War. And I think Bucky fans would be devastated if he straight-up murders Tony.
IF Bucky does kill Tony, I think it will be either in the heat of battle, or because his brainwashing has been triggered. The shooting name of Civil War is Sputnik - which in the comics is the trigger word for Bucky. I doubt that’s a coincidence. So yeah, he could easily be the “Sharon Carter” of the MCU. (Though, I will admit, my fantasy outcome is Sharon assassinating <whoever ends up dying, if anyone> and its not brainwashing, but Sharon is actually a deep-cover Hydra agent. Actually, I’d LOVE to see Sharon Carter end up being the MCU version of Synthea Schmidt, but that’s a whole ‘nother kettle of fish…)
There’s a lot of what-ifs flying around that really just can’t be answered until we see what happens. There’s obviously a big difference in how the characters would react to assassination vs KIA, for example.