The hash that comes out of a strong hashing algorithm has a random distribution. Although it is less likely, it doesn't take any more work to find a 000000000000000001.. hash than it does a 0000ffff.. hash, only luck.

The blockchain requires each block to meet the proof of work. To replace ten past blocks, you would have to generate ten blocks of your own. This is a much higher bar than a single lucky hash being able to replace ten blocks.

With a more-difficult-hash chain instantly winning like proposed, it would be an orphan free-for-all, you could get one lucky hash attempting to build on blocks from a week ago and replace tons of transactions. As described, a miner could attack for free by

1. constantly be transferring a large balance between new addresses in every block they mine,
2. find a "lucky" hash much smaller than the average and withhold it, and
3. make all sorts of purchases that will be wiped when they publish the chain-erasing block find that sends the money back to the miner.

OP already annoyed everyone with his great ideas based on a poor understanding of mining here: https://bitcointalk.org/index.php?topic=823544.msg9204175#msg9204175