My science teacher is very scariest man because he is very vicious.
So he is very bad science teacher.
Here's your corrected composition, Jimmy. Please take a look at the corrections below. Good night! 
Who's currently the scariest man alive and Why?
My science teacher is very scariest man because he is very vicious.
So he is very bad science teacher.
>>> My science teacher is the scariest person I know - he's incredibly harsh and intimidating. He's so mean and terrifying that it's hard to focus in class, so I believe he's not a good teacher.