This Poliwrath (nicknamed Poli) is Red's very first Pokémon that he obtained during his early childhood when it still was a Poliwag.
Red met Poli as a Poliwag in a lake. When Red drowned, Poliwag evolved into a Poliwhirl and saved his life. Since then Poli is Red's partner.
He saved his life once more from drowning into the ocean in the eleventh chapter when Red once did when Lt. Surge pushed him and his Poliwhirl off the boat and Poliwhirl evolved into a Poliwrath saved him and they went back on the boat. He helped Red many times in his life such as defeating Blue's Charizard in the Pokémon League along with Pika.