根本

My ideas rocked her assurance to its foundations. / My ideas shook the basis of her belief.

be identical at root; be essentially the same

tackle a problem at its source

get to/at the root/essence/core/heart of a problem; seize the essence of a problem; grasp the essentials of a problem

get at/to the root of sth; get/go to the heart of sth; go straight to the heart/root of sth

cardinal principle

root/bottom/basic/fundamental cause

fundamental matter; substantive issue

fundamental contradiction

fundamental interests

ultimate way out

fundamental/thorough change

I didn't enjoy this song at all.

He is no doctor in the first place.

It's not half as bad as you made it appear to be.

That is no place for a child.

simply do not treat sb as a human being

I totally disagree.

The matter has been settled once (and) for all.

fundamentally change the attitudes towards education

be diametrically opposed to each other

I've never seen him before.

Selfish interests don't weigh with her at all.

He is quite above such conduct.