It's not a really a good idea to 'destroy' people and especially not enemies. Enemies are more important than friends when it comes to doing things in your life. Enemies are the reason you strive harder for success. Having said that, there will be times where your enemy is better than you and you need a little bit of a psychological advantage. You can certainly weaken your enemies with a few tactics and play with their emotions a bit without actually harming them.
Again, there is no guarantee that they'll be weakened or be defeated. In the end, it's your grit and talent that'll help you win. Here are the things you can do to demotivate and defeat them:
1. Make yourself appear more loved than you are: Showing yourself as a more loved person is one of the most effective ways of demotivating your enemies. Have a large social circle, look good and always have a smile on your face. Nothing irritates your enemy more than you being happy, loved and good-looking.
2. Always know more than you should: If your enemy is above you in a hierarchy then you will need to be smarter and more clever than him/her. Strive for knowledge and find it any way you can. Knowing more information gives you an undeniable amount of advantage over the person you're trying to cross.
3. Be proactive: Take initiatives, communicate more, and get noticed by important people. Proactivity attracts more attention than hard work.
3. Don't fake too much: The above methods hold true with the quote 'fake it till you make it.' Don't fake a lot or your enemy will know and not pay attention. You need your enemy's attention on you all the time.
4. Make him your friend: The best way to defeat your enemy is to make him your friend. Turn your enmity into a positive rivalry. Try and get along with him. It's not always possible but it certainly is effective.
Last but not least:
5. The biggest enemy is 'YOU': You are your own biggest enemy. Others are there for some time. Get yourself under control first by changing your mindset, setting goals, improving every facet of your life,and loving yourself more.