If you take a little time to read through the threads on this site you'll find that trying to sabotage another site is frowned on.
It's also a bit of a dangerous thing to try. The main way people think of is to do an overly excessive backlink building campain. While it's true that being way to aggressive could get a site sandboxed, there's also a chance that you'll just create a really successful campain for your competitor and make it even that much harder to beat them. The other way to try it is to start making backlinks to their site in "bad neighborhoods". This might seem like a better strategy, but google is aware that this goes on and tries to identify when it's happening. Again your efforts to damage your competitors rankings could inadvertently have the result of helping the site's serp listing more than harming it.
Overall you efforts are probably better spent trying to improve your site rather than harm someone elses.
You also don't always know who owns a site. What if it's another member on bhw who's site you ready to trash.