What are some of the actions associated with religious extremism?

While you did not provide a list of possible actions, one can safely assume that different types of religious extremism (e. g. christian religious extremism or buddhist religious extremism) can lead to many horrible things. A classic case of this were the crusades where the christians from Europe amassed big armies that were supposed to go to the Middle East and reclaim it from muslim rule - this is one of the biggest and most horrible examples what religious extremism can do as it led to a slaughter of thousands of people on both side. Another example are buddhist killings/burnings of the muslim populace in Asia.