Zealot (noun)

1. A person who is fanatically devoted to a cause or religion.
2. A person who is willing to act violently or take extreme measures to defend or promote their cause or beliefs.

Origin:

From latin zelotes, from greek zēlōtēs, from zēlos "zeal".

Examples:

1. He was a zealot for the revolution and would stop at nothing to see it succeed.
2. She was a religious zealot and would not tolerate anyone who did not share her beliefs.
3. The group was made up of political zealots who were willing to use violence to achieve their goals.
4. He was a zealot for the new technology and would not listen to any criticisms of it.
5. The organization is run by a group of environmental zealots who will not compromise on their beliefs.