Because of the inherent properties of block chain code, you cannot delete all your activity. Or any of it for that matter.

So it looks like what you want to do is to take your money and just abandon your Steemit account.

Look into transforming your Steem and Steem dollars into Steem.

Then convert that Steem into Bitcoin using an exchange such as Bittrex

Your last step will be to either convert your Bitcoins and send them to your bank account or use these same Bitcoins to purchase something on the Internet.