This is the 5603rd most frequent Japanese word.
ことごとく
Entirely; without exception.
In this sentence, “ことごとく” means that every one of his proposals without exception was rejected.
彼の提案はことごとく否定された。
All of his proposals were rejected.
Here, “ことごとく” indicates that no part of her story left him doubtful.
彼女の話を聞いて、彼はことごとく納得した。
After listening to her story, he was completely convinced.
This usage of “ことごとく” suggests that all of the facts, without exception, were not in his favor.