When this thing comes down on turn three, you know your opponent needs to remove it. Otherwise, it will keep growing each draw step and make more 1/1 tokens.
The longer it takes your opponents to deal with Nadir Kraken, the fewer chances they will have to deal with it. Eventually, it will do so much damage that there is nothing left for your opponent to do.
Be sure to make Nadir Kraken your first pick in Draft. and look out for more draw spells along the way.