Word/expression for someone who doesn't reciprocate favors?

Fair-weather friend (noun) A person who stops being a friend in times of difficulty.

(Oxford Dictionaries)

• I have helped Peter a lot when he had issues, but he stiffs me when I am going through a tough time. I thought he would help me, as I had helped him a lot in the past. He is a fair-weather friend. [Someone who doesn't reciprocate favors].

He's ungrateful:

Not feeling or showing gratitude.

It's not narrow enough; but it's close.

self-centred Merriam-Webster

preoccupied with oneself and one's affairs, concerned solely with one's own desires, needs, or interests. "he's far too self-centered to care what you do"