The telling lyrics: "Did you think we’d be fine? / Still got scars on my back from your knife / So don’t think it's in the past, these kinda wounds they last and they last now / Did you think it all through? All these things will catch up to you / And time can heal but this won't, so if you’re coming my way just don’t / Oh, it’s so sad to think about the good times, you and I"
Who it's supposed to be about: Katy Perry
Why? Swift started this one when she told Rolling Stone a story about a fellow singer she realized was her "straight-up enemy," and as if in response, Perry tweeted, "Watch out for the Regina George in sheep's clothing." Here's a full rundown of the feud, which only seemed to get worse with the release of the "Bad Blood" music video.