radical

radical: of or going to the root or origin; fundamental.

rad·i·cal·ness, noun
—Synonyms 1. basic, essential; original, innate, ingrained. 2. complete, unqualified, thorough; drastic, excessive, immoderate, violent. Radical, extreme, fanatical denote that which goes beyond moderation or even to excess in opinion, belief, action, etc. Radical emphasizes the idea of going to the root of a matter, and this often seems immoderate in its thoroughness or completeness: radical ideas; radical changes or reforms. Extreme applies to excessively biased ideas, intemperate conduct, or repressive legislation: to use extreme measures. Fanatical is applied to a person who has extravagant views, esp. in matters of religion or morality, which render that person incapable of sound judgments; and excessive zeal which leads him or her to take violent action against those who have differing views: fanatical in persecuting others.
—Antonyms 1, 2. superficial.