Rez HD

You unlock "Lost Area" after finishing Area 5 in the normal game. Just finishing lost area should net you the achievement. If you can't complete the game try to get the Rezident achievement first so you will unlock more forms and you can get hit more before you go game over.

If you have problems with getting the score try to do chain hits instead of single hits. Doing chain hits nets you more points. There is no boss in this area so don't hesitate in using overdrive whenever you feel overwhelmed by enemies.