Idiom or phrase for "getting hatred/abuse after giving care to a person"

There ain't no justice.

From The Big Apple (an etymological dictionary):

"There ain’t no justice” is a phrase that dates to at least the 1850s. “There Ain’t No Justice” was the title of several “Moon Mullins” newspaper comic strips in 1924, the title of a book in 1937, and the title of a movie in 1939.

“TANJ (There Ain’t No Justice)” is from Larry Niven’s science fiction novel, Ringworld (1970). “TANJ” has expanded beyond science fiction and has entered common speech, especially for computer users.

The shortened form (TANJ) has been used in science fiction and other forms of popular culture, in particular as a kind of curse.

It essentially means that life isn't fair. If life were fair, you would expect good things in return for doing good things.

No good deed goes unpunished:

Due to the cruelty, ignorance, or selfishness of the world or others, one's good deeds or good intentions will often result in more trouble than they are worth.

[The Free Dictionary]

You have your love thrown back in your face.

Throw something back in someone’s face:
To behave badly towards someone who has been good to you

Example: He threw all her kindness back in her face.
[Macmillan dictionary]

Your son throws your love back in your face.

The road to hell is paved with good intentions

Well-intended acts can have disastrous results, as in "She tried to help by defending Dad's position and they haven't spoken since-the road to hell is paved with good intentions".
[The Free Dictionary]

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Wikipedia:

... that good intentions, when acted upon, may have unintended consequences

Another day older and deeper in debt

This is a well-known song lyric from "Sixteen Tons", originally written in 1946 and recorded dozens of times by various artists. It describes the plight of a coal miner who does honest, hard work, but whose only reward is to get older and poorer. This lyric is a well-known line from the song, and describes the notion of doing good, hard work with only negative outcomes.

You might say that they bit the hand that fed them.

bite the hand that feeds you to act badly towards the person who is helping or has helped you - Cambridge Dictionary

Here are a couple of examples in print:

• Everybody knows how helpful you have always been to her, but she bit the hand that fed her. - 1001 idioms to master your English

• Of Geoffrey's other illegal appointees to York, [M]r Erard, who had known Geoffrey when he was chancellor, also bit the hand that fed him, being a member of the hostile mission of the dean and chapter to Rome in 1194. - English Episcopal Acta 27, York 1189-1212

a snake in (one's) bosom

Someone whom one has befriended, taken care of, or treated well but proves to be traitorous, untrustworthy, deceitful, or ungrateful. (Used especially in the phrase "nourish/nurse/nurture a snake in one's bosom.")

Well, it turns out that Margaret was quite a snake in my bosom. I put my neck on the line to get her a job in our company, and then she turns around and tries to get me fired!

I thought our love was not only mutual but indestructible; and yet, I have nursed a snake in my bosom all these years: my darling husband has cast me out and run off with a younger woman. https://idioms.thefreedictionary.com/snake+in+one%27s+bosom

I don't get no respect

This was the comedian Rodney Dangerfield's tag line and began some of his jokes. They were often about how people despised him for no special reason. Not the funniest one, but an example: "With my dog I don't get no respect. He keeps barking at the front door. He don't want to go out. He wants me to leave".

There was a time when everyone had seen him in Caddyshack or starring in Easy Money and would recognize it as a Dangerfield reference. It roughly meant "do you see what I have to deal with?" but with a softer tone.