彼の母親は可哀相だ。あいつときたら母親泣かせもいいところだ。

English Translation

I feel sorry for his mom; he really puts her through the wringer.

What is the usage of 良いところ in this sentence?

いいところ means “a good thing” or “the right moment” according to my dictionary.

So I think the sense is “when it comes to that guy, the tears of a mother are completely spot-on”.

I see, thank you! Do you know why 母親泣かせも can be said as such, instead of 母親泣かせも?

I have found 親泣かせ in my dictionary, with the meaning (as a name or -na adjective) “making one’s parent cry” or "disgraceful child.

Also, ~泣かせ is a suffix that can be added to a name describing people , with the meaning “embarassing or troubling terribly” said people. And in addition someone that embarass or troubles said people.

So, yes I think the word is used as a noun here, not a verb.

I have found another expression that might be related to this:

と言うところだ which apparently has a similar meaning to もいいところだ

https://jlptsensei.com/learn-japanese-grammar/というところだ-といったところだ-iu-tokoro-da-meaning/

So I would revise my translation a bit, saying that “when it comes to that guy, he is nothing more than a disgrace to his mother” would be more accurate.