All the more; even more — indicating that something becomes stronger or more so because of a reason or circumstance.
雨で道路が濡れて、なおさら滑りやすくなった。
Because of the rain the road got wet and became even more slippery.
彼女は努力している。だからなおさら尊敬されるべきだ。
She works hard. All the more reason to respect her.
説明が不十分だったので、なおさら混乱が生じた。
Because the explanation was insufficient, confusion increased even more.
Used with a negative verb to mean 'all the less' or 'even less', i.e., something becomes even less likely or possible.
失敗してしまい、なおさらやる気が出ない。
Having failed, I feel even less motivated.
詳しく聞いても、なおさらわからなかった。
Even after asking in detail, I understood even less.