radical

A person who advocates for thorough or extreme political or social reform, often departing significantly from conventional or traditional views.

• The party was concerned about the growing influence of the radical elements within its ranks. — The political group was worried about members with extreme views.
• He was considered a radical for his revolutionary ideas on education. — His revolutionary educational ideas made him seem unconventional.

Relating to or affecting the fundamental nature of something; far-reaching or thorough. It can also describe something extreme or drastic.

• The company implemented radical changes to its organizational structure. — The company made very thorough and fundamental changes to how it was organized.
• A radical solution was needed to address the root cause of the problem. — A fundamental and drastic solution was required to fix the underlying issue.
• The new art exhibit featured some truly radical concepts. — The art exhibit showcased very new, extreme, or unconventional ideas.