Rosy Moonlight

I think it would have been better if Sunny had a more difficult life.

Argyle also didn't really believe in Ponykind Unity but still humored Sunny because she was his little girl and he never had the heart to "correct" her, not realizing what kind of effect it could have.

He would have died when Sunny was like 10, and Sunny would have grown up under Phyllis' care.

Sunny would've been even more horrified by Sprout destroying the watch tower, feeling like she was watching her brother destroy her childhood home.

Then, knowing that Sprout is on the run, and Phyllis, the only mother figure she can remember, being in jail for effectively being an accomplice to crime.