Porky in his Spider Machine.
"Why is it you struggle to cling to life with such puny minds, pitiable bodies, and feeble hearts? -Porky, Mother 3
Porky is a character that has been in all of the Earthbound/Mother games. In Earthbound, Porky is Ness' neighbor and belongs to a rich family. Ness helps Porky find his brother late at night so he avoids trouble. Later, Porky becomes greedy and enraged. He later takes over and is constantly on the run.
In Mother 3, however, Porky is the main antagonist, and he is Lucas's arch-nemesis. He is certainly behind the whole catastrophe that fell in the Nowhere Islands. Near the end of Mother 3, Lucas, Kumatora, Duster and Boney go on a wild chase through Porky's Empire in New Pork City. When they reach the room, Porky is seen as a blue-ish gray man. He has white hair and a white beard. His eyes aren't visible, as the hair covers his eyes. He is laying down in a device that relates to the Spider Machine used in the Earthbound game.
Porky is in poor shape do to the abuse of time travel. He has the appearance of a young man, but he states he is older than any human. Another thing is that he is immortal. As long as he has his Spider Machine and Absolutely Safe Capsule, he will be just fine.
Dr. Andonuts explaining the Absolutely Safe Capsule.
So, in the end of Mother 3, there is no killing Porky. As Dr. Andonuts stated, once going into the Absolutely Safe Capsule, there is no leaving it. Porky continues to taunt Lucas and his team while they continue. He even survives the destruction of the Nowhere Islands.