[adverb]Many senior legal figures believe the system is fundamentally flawed (= has very serious faults).Our new managing director has reorganized the company a bit, but nothing has fundamentally changed/altered (= its basic character has not changed).I still believe that people are fundamentally good (= are basically good).I disagree fundamentally (= in every way that is important) with what you're saying.
FUNDAMENTALLY
Meaning of FUNDAMENTALLY in English
Cambridge English vocab. Кембриджский английский словарь. 2012