The term "fanatical groups" refers to extremist organizations with strong and extreme beliefs. Some alternatives for this term include radical organizations, zealot groups, extremist sects, fundamentalist movements, and militant factions. These groups often have intense and unwavering devotion to their causes, which can lead them to commit violent acts and seek to impose their views on others. It is important to note that not all groups with strong beliefs are fanatical, and the term should be used carefully and with consideration for the potentially negative connotations. Ultimately, it is crucial to be aware of the potential dangers posed by these groups and to approach them with caution.