Hearthpwn

This is my refined list that managed to score a win against the king himself. 

Similar rules apply as with other decks, you need Enter the Coliseum by turn 7, and Kel'Thuzad plus 1 or 2 Shieldbreakers by turn 10. 

Those are the only two MUST haves, the second one can wait for a few more turns if you can heal up while cycling through the deck.

Focus on staying alive and having the board whenever possible, the rest will just happen by itself.

Do your best not to give the last lost soul any chance of dying before your OTK is in place. For example, don't summon any minions between Coliseum and Kel that might end up ruining your game. 

Have fun and don't be afraid to ask for help if needed. I will post updated decks for every boss I couldn't beat with the decks that already exist here on the site.