Abandoned Spinel.
Killed other gems to save her colony.
Never told her friends about her true self.. well, even though Pearl knows.
Bubbled Rose Quartz for being.. well, Rose Quartzes.
I think it's obvious that Pink.. is quite the villainistic character. I mean, it's possible that it was from the other Diamonds old ways; but before all that, she was quite a... well.. brat. As Volley said, "would throw tantrums left and right. She had a scream that could crack the walls." If I was a 5 year old with a scream as loud as Black Canary's, I would worry about having those faint memories. And so, I would worry about her. All of these things that Pink Diamond is capable of is... quite troubling.
Let me know your thoughts