1. Flayed Alive  Being flayed alive would have been a far greater punishment than being eaten by dogs. He probably was dead in what, one minute? Two tops? While being flayed takes hours, days even if it’s done right, with the flayed being in unimaginable pain the entire time. Though knowing Ramsay, he might even enjoy it.
  2. Eaten By Ghost  This one would have been more symbolic than anything while being just as gruesome and grisly as being eaten by the hounds. Being eaten by Jons dire wolf would have been a good message to send to the North, showing them that the Starks are back in business. Plus, all the menacing wolfs have been getting murdered left and right, so it would have been nice to see Ghost have his time to shine.
  3. Trial By Combat  Though this is by far the most merciful of the others on this list, it would have been awesome to see Jon disembowel Ramsay on a one on one fight. No bows or anything just sword on sword. Maybe give Ramsay two of his hounds and give Jon his dire wolf. That would have been an epic battle and an excellent way to prove to the other Northern lords that the Starks are more powerful than the Boltons.
  4. Executed By Theon  Now, this is one of the more improbable ways, but still, it might have happened. Sansa and Jon could have held Ramsay prisoner until meeting with Theon in the future and then hand Ramsay over to Theon to do the beheading or whatever Theon would like to do to him really. Theon has more of a right than Sansa to kill Ramsay by a lot. Ramsay cut off his genitals, flayed off his fingers and toes, starved him, tortured him, and made him a slave. It would have been an amazing way for Theon to finally put his past behind him and start over.
  5. The Next Reek This would have been by far the best way to punish Ramsay, by turning him into the next Reek of Winterfell. This means giving him the full Reek treatment including the flaying and the removal of his genitals and all. Death is just mercy that a creature like Ramsay does not deserve. Make him live in the same conditions as the past Reek, make him suffer like all those that have suffered under him until the day he dies. This would have been the most appropriate way for Ramsay to be punished.