Generally speaking people and groups that believe this have a hard time fitting into society and on occasion are known to do terrible things to groups they dislike. For example, the Nazis were an Aryan race supremacist group and held that the Germans were the 'master race'. They then set out to murder or enslave everyone else. See: holocaust.
Although not specifically considered to be supremacist groups. Terrorist organizations such as Al-Qaeda and groups occasionally associated with terrorism such as the Palestinian Liberation Organization display traits often associated with supremacist groups. Examples of these traits are the spreading of Anti-Semitic propaganda and advocacy of religious states.
Sometimes groups such as these try to hide behind political causes, making them difficult to identify as supremacist groups.Supremacist Groups
Supremacists and Terrorist organizations