A renowned FBI agent must stop the world’s most powerful man before he brings the planet to the brink of environmental destruction.

I think that there have been billion of movies like that. What makes movie original? Your logline applies for half of a Hollywood adventures.

Who is most renowned agent of the movie world? James Bond. I would try to restrain from this word.

This genre is so profaned that it's very hard to come up with something new. Good luck mate

What makes the world's most powerful man the world's most powerful man? Is he intellectually powerful? Is he physically powerful? Combination? Does the hero have a flaw which could make it extremely difficult for him to defeat the world's most powerful man?

I like it so far, but it feels like a situation.

What you wrote, feels like it's just the first scene in your story. You know, an agent is briefed (with the exact words you wrote). What I am missing from the logline is the second part -- the specific mission, such as, infiltrate and assassinate the most powerful man.