Whats the characteristic/personality of one that rewards those who treat him well, while punishing others who don't?

I'm looking for a word instead of a phrase to describe this, thanks! Greedy and Selfish don't really fit for what I'm looking for.

Such a person is called discriminatory or biased.

WordHippo defines discriminatory as

Making or showing an unfair or prejudicial distinction between different categories of people or things, especially on the grounds of race, age, or sex

In your description, the person shows an unfair distinction on the basis of whether people treat him well or not.

e.g. I think it was also discriminatory against those who do not own a sense of humor.

Here is an example with biased (which means to exhibit bias, prejudice for or against one person or group):

Examined from the learner's point of view, the standard approach is heavily biased against beginning students. (See WordHippo for more examples)