This is the 808th most frequent Japanese word.
きっと
Certainly; surely; undoubtedly.
In this sentence, きっと conveys a strong sense of certainty or confidence about the speaker's belief.
きっと彼は来ると思います。
I'm sure he will come.
Here, きっと is used to express the inevitability or strong likelihood of success as a result of the listed effort.
もし努力すれば、きっと成功するでしょう。
If you make an effort, you'll surely succeed.
In this context, きっと emphasizes the speaker's assumption or deduction given the situation observed.