thanks in advance!!!

[sympathy]

Hi , I have a question on word usage.
How do you describe a person who does this to someone else ?

Let's say the person is in authority, or a boss, or a teacher ... For some unreasonable reason, he hates someone, and then he always wants to harm that person. For example, the teacher doesn't like one of his student, and he always gives the student difficult math problems to make his grade go down, or he can take off some marks of the student just because of the student's bad handwriting. Or he always criticizes that student before other students. That teacher won't let the student eligible to participate in a math competition. In class, the teacher always restricts the imagination of the student ... Everything is unreasonable ...

In other words, in political language, we use 'crackdown', 'suppress', ''crush', 'clip wings' ... but how about more commonly used words in normal conversation ?

[Tdol]

How about pick on?