I had this thought earlier today, and I thought to share. In "On the Run" we see Pearl and Amethyst fight for (I think) the only time in the entire series. Pearl briefly toys with her, before asserting that Amethyst can't win. Then Amethyst pulls out a double whip electro power move (patent pending) that throws Pearl back, and then breaks down into tears, along with the audience. I think it's a safe assumption to make that Pearl is the stronger of the two gems, a claim that Amethyst didn't refute (she just didn't care). What does this mean?
Well, we recently got confirmation that Pearl isn't like Garnet or Amethyst, she's a gem with a purpose, and apparently useless on her own. Beyond that, she said in "Sworn to the Sword" that she wasn't built for fighting. This all ties in nicely with the "Pearls are a servant class" theory that has a lot of traction in the fandom. Conversely, Amethyst was made in the Kindergarten. Amethyst was made for a purpose too, but we don't know it yet. I don't think it's a stretch to say she was supposed to be a soldier, but got "overcooked" and left behind.
Putting two and two together, Pearl, a gem that isn't built for fighting, is stronger than Amethyst, a gem that, arguably, was. Amethyst must be uniquely weak when compared to other gems. Even in other battles, like against Lapis and Steven's watermelon's, Amethyst gets soundly beaten.
Whatever "overcooked" means for Amethyst, it seems that it weakened her immensely when compared to what she could have been.