Cleaning the shower is the absolute worst, no contest. But see if you can top it with your own worst chore.
  1. Cleaning the shower
  2. Doing the dishes
  3. Cleaning the flat stovetop
  4. Cleaning behind the refrigerator
  5. Folding all the laundry.
    Suggested by   @amieshmamie
  6. Cleaning the litter box
    Suggested by   @kaitmaree
  7. cleaning the shower drain
    Suggested by   @jennyfricke
  8. Specifically, loading the dishwasher.
    Suggested by   @classyAF