article "the" needed in this sentence or not

• I feel very sorry for the people who have to live in the cities which they absolutely hate because they have no choice.

As I seee it, in this case, with respect to the first "the" you are more likely to presuppose that the possibility of such individuals that have to submit to the stated situation has been mentioned in the discussion or that this situation is one that is recognised as extant; you could hardly write "I feel very sorry for the people who have to live in cities which they absolutely hate because they have no choice, if there are any such people.".

This seems perhaps more evident from the following simpler sentence.

"I'm sorry for the animals that fall into that hole, if any do."

It seems that you wouldn't readily say that in English but rather something like "I'm sorry for any animal that should/could fall into that hole.".

Again as I see it, the second use of "the" is only justified by a very particular context; that is to say, normally, we'd say or write this:

• "I feel very sorry for (the) people who have to live in cities which they absolutely hate because they have no choice."

By the use of the determinative "the" with "cities" one appears to presuppose that there are for all persons on earth cities that they hate, whereas this is no common knowledge; it is probably the case that for a great number of people there aren't any cities that they particularly dislike.

In the case of plural countable nouns, the the is often optional. It is usual to include it when the noun is defined in some way.

In your case, "the" people is encouraged by "who have to live in the cities" - the noun "people" is defined, and the the in "the cities is encouraged as "cities" is defined by "which they absolutely hate."

This defining allows the use of "the" as "the" (a determiner) is basically a demonstrative adjective closely related to "that/those".

I would therefore include both.