If the creature's power is greater than 2 as the activated ability tries to resolve, the ability won't resolve and none of its effects will happen. However, if instead the creature's power is raised above 2 after the ability resolves, it still can't be blocked that turn.
Random a card of Magic: The Gathering (MTG), but you can also roll the D20 dice, random a Planeswalker, have fun with the random rules and more.