The winner of this category is Aquamarine!!! Aquamarine can bring anger down from 100% to 70% (while wearing a well cleansed and maintained piece. Can't vow the same for those that are not activated and not properly cleanse regularly). It is also strong at cleansing negativity from our body.
Howlite is also an extremely calming stone. However, it focus more on calming the mind and possible to make some feel sleepy as its one of the best stone for insomnia.