proof: https://imgur.com/a/BbKsf

To get the title you need to win the game with negative health. It’s possible to achieve if you bring the health of your oponent and your own to a negative value in the same moment. Note that your health can’t be lower than your enemy’s. If you create a draw with both of you having negative health it will be counted as your win. I finished with a nice -1 vs -1 score

How to do it?
As for now there’s only one card that lowers the health of both opponents at the exact same moment – Afflicted Alit. In order to get the title yo will have to drop Afflicted Alit when both of you have 1 health left (probably also you can have 2, so you end up having 0, can’t promise though).
To achieve this goal you need to have control over the board as much as possible. Also there’s a huge amount of luck required too You can have perfect situations just to see your enemy conciding when you’re sure you’d nail it…

In the deck I used there are plenty of reach effects hitting for 1 (Sharpshooter Scout and Valenwood Huntsman), for 2 (Afflicted Alit and Ice Spike), for 3 (Crushing Blow) and for 4 (Lightening Bolt)
You will need plenty of draw to get the cards you need – Rapid Shot, Ice Spike and Tome of Alteration
To keep the control over the board you have all the ping cards and spells, plus huge removal like Burn and Pillage, Cast Out and Goldbrand
Note that sometimes you’ll find it useful to bounce back some minions to your own hand with Cast Out and Forsworn Guide for the Summon Effect

All you need now is to race your enemy down quickly then force your enemy to damage you as much as YOU want by removing apecific minions from board. If situation gets dangerous reset the board with Burn And Pillage. Try to keep as many reach cards in your hand as possible to adjust the final health for both of you before droping Aflicted Alit on board.