When you see obliterate, think of evil alien invaders that zap a planet with a destructive ray. In one blast, the planet and all of the people on it are vaporized. The planet is truly obliterated, or completely wiped out.
A long time ago, obliterate had to do with blotting out words on a page. This is why you see the word literate in there. Today it means to erase or destroy completely so that there is nothing left. While you can still obliterate text, you can also obliterate hope, an opponent, or all traces of your presence. Whatever you obliterate is completely gone.