Kill the wall

vk.js

// Use with http://vk.com/dev/execute
var owner = ; //your id or public id * -1 

var items = API.wall.get({owner_id: owner, count: 100}).items;
var c = 0;
while(c < items.length){
    API.wall.delete({owner_id: owner, post_id: items[c].id});
    c = c + 1;
}
return items.length;

Execute until retval = 0