Android 16 is something of a puzzle. Created by Dr. Gero, he's big, bulky and quite powerful and sets out initially to help Gero destroy the Earth. In fact, 16 was created solely to destroy Goku after Dr. Gero realizes just how disobedient 17 and 18 are. Android 16 lies dormant until 17 and 18 resurrect him but once out, he discovers the beauty of life. Its his death that spawns Gohan into his ascension that ultimately allows him to defeat Cell.