well apart from bosses the strongest mob in town are you or a multiplayer friend oh what a wreckage can you do with spawing bajilions of creepers,withers,zombies,skeletons,tnt,flint and steeling a whole jungle ... ohhh the chaos you can make with just a click of a mouse
Zombie Pigmen. Only mob that can't be dealt with just by spamming your sword (enderman), standing there and watching it miss as you shoot it (ghast), and standing there and shooting it as it finds itself unable to damage you in your Fire Prot IV. armor (blaze).
They are disproportionally strong. They are small and but are unstoppable, fast, chase the players down to the hell and can deal a lot of damage. It can kill the player with 3 hits or less. Try to kill one with bare hands to get an idea.
When I discovered their "special" properties, I spent hours messing around, playing tag, and wrecking down villages. Below is an example: