Not a WorstSong because it's not a bad song, but a notable mention goes out to Kathy Perry's "Chained to the Rhythm," simply because it should so, so, SO obviously be "Chained to the Melody" instead. "Melody" rhymes with the previous line ("Drink! This one's on me"), it fits the rhythm much better, and more easily segues into her hook-ending vocal flourishes. That hook features very slapdash lyrics overall, performed in a stilted, jarring cadence--the opposite of rhythm--but the biggest flaw is the fact that the songs screams to be "Melody." The song's most important word is the wrong word.
(The song's exceptionally vague, nonexistent "political" message remains unaffected by this change.)
Shame to see Sia cowrote this song seeing as she has such an ear for melody. The move suggests either exhaustion on Sia's part, releasing scads of her own music as well as writing scads more for other artists, or just classic crabs-in-a-basket sabotage, Sia realizing she can give away her worst material, or even purposefully ruin what would have been a decent pop song by sullying the integral word. Kathy meanwhile does what she's told, as she always has, since she was Kathy Hudson, pretend Christian pop artist, and gamely sings what is very clearly the wrong word.