I wanted to translate a simple sentence which is "what I fear the most is to be unsuccessful". I check with google translator and realized I made a mistake. The Google translation is 我最害怕的是不成功. I do not understand the role of 的 in the sentence. Can you help me please ?
"我最害怕的" here is like a noun clause. It means "what I fear the most". Entire sentence means: What I fear the most is not succeeding (or "unsuccessfulness" but not sure if that is an English word).
As for why it means as such, here is my understanding. Disclaimer: I am not a linguist and I do not work in the education industry.
"的" is the assistive word (particle) that marks an adjective. If not using like this, it could comes as "我最害怕的事情" (the thing/event that I fear the most), omitting "事情" makes it more general, i.e., "what I fear the most" in any scope, not limited to a thing/event.
Another examples: "我怀念的是无话不说" (lyrics of 《我怀念的》, i.e., What I Miss, by Stefanie Sun).