Extreme hatred and anger are usually the results of some very deep unresolved emotional issues that have been burried and repressed for years on end. These could be toward people, places or things (circumstances). These are TOXIC! and besides hurting those around you, you can destroy yourself from within as they take over every aspect of your life and you see nothing but "doom & gloom".
If this is with either yourself or someone you know, the best lifeline going these days is not necessarily long term visits with a counselor or prescription drugs that just mask these symptoms, but instead, take control of your life by looking into and learning Emotional Freedom Technique (EFT). It's hands down, the most effective self applicable technique that can not only uncover, but eliminate any and all negative feelings and emotions. This can be learned either via on line or with a one time visit to a practicioner in your area and you're home free...of course you have do do some work on your own, but it's the one "magic pill" for all these seriously dangerous emotions that make living life a real hell. Life is supposed to be fun and full of happiness. This stuff works, and is boasting of a 98-100% effective rate. Nice thing too is that no one need know what you're doing for yourself..they'll just see the results. Bet you can't keep it to yourself though