Piccolo

Piccolo is a Namekian who lives on Earth. He loses relevance after the androids are introduced, and is all but forgotten shortly after Next Generation begins. He too, suffers from his power level being restricted due to his Namekian limitations.

Biography
After having been born from an egg shortly after King Piccolo was killed by Son Goku, Piccolo grows up with little more than hatred for the planet. Living off of insects and invertebrates, Piccolo grows and his power rises. He begins eating humans once his power level matures, but he runs into the United Government's military. Being hurt by its weaponry, Piccolo feeds on humans in secret, to the point of becoming impervious to gunfire. At that point, he is bombed. This is told to Goku vaguely as he is growing up with Grandpa Gohan.

By the time Goku becomes an adult, Piccolo is nearly impervious to human weaponry.