1) At bottom 2) At heart 3) Au fond 4) Basically 5) Crucially 6) Essentially 7) In essence 8) Mainly 9) Very 1) Au fond 2) Basically 3) Essentially 4) In actual fact 5) In effect 6) In essence 7) Really 8) To all intents and purposes 
• (adv.) Primarily; originally; essentially; radically; at the foundation; in origin or constituents.
Fun`da·men'tal·ly adverb Primarily; originally; essentially; radically; at the foundation; in origin or constituents. ' Fundamentally defective.' Burke. 
fundamental, fundamentally 1. Of or relating to the foundation or base; elementary: 'We studied the fundamental laws of the universe.' 2. Forming or serving as an essential component of a system or structure; central: 'He presented an example that was fundamental to the argument.' 3. Of great significance or involving a major change: 'This is a b...