Beast Within Achievement in Magic: The Gathering - Duels of the Planeswalkers 2013

Celestial Light, a deck centered around gaining extra life, has a card called "Ajani's Pridemate", that for every time you gain a point of life it gets +1/+1. Using that method is the easiest way to unlock the achievement, however you can also just play any other deck and use enchantments, artifacts, or instants, to boost the creatures power over 10 by the time you win.