Just like in regular Minecraft, there are pigs, but there are also pigs that explode, and pigs that eat almost any mobs, inxluding its own kind! This page is about the latter.
A Cannibal Pig is a carnivorous variation of the pig. Cannibal Pigs are larger than ordinary Pigs, and look similar to wild boars. Cannibals will attack other nearby mobs, and yes, even Steve, when hungry.
It is recommended to use Bows and Arrows to fight these big bruisers. You can also use another hostile mob to distract them while you either run for the bally hills, or despatch them both.
Cannibals will attack other mobs if near it, so distract it with several snowman (also called snow golem) towers. Check out the Minecraft Wiki for more information on Snowmen.