Android 16 is an android programmed to kill Goku, but he loves the earth. He thinks it's beautiful, and then no longer has any means even to think about Goku. He hardly says anything to him during the Cell games. He gets pretty banged up by Cell, but Krillin helps him and takes him to Bulma's to be fixed up. When he is repaired, he is ready to help fight Cell. He jumps on Cell, ready to self-destruct with him, but he doesn't have his bomb inside him, Bulma took it out because she didn't want to take any chances in case he went back to the wrong side. So Cell attacks, and he ends up with just his head. He talks to Gohan and tells him to let it go (his power), then his head gets stomped on by Cell, and that's the end of 16. It's that act that releases Gohan's rage.