The article is about the Abell 1201 black hole. The paper referenced in the article is paywalled though[0].

And Wikipedia has a List of most massive black holes[1]. Quite fascinating, although the list is about their masses and not their sizes.

I'm not an expert on the subject, but the Abell 1201 black hole and the others in the list are near the theoretical limit of a black hole's mass (5 * 10^10 solar masses).

[0] https://academic.oup.com/mnras/article-abstract/521/3/3298/7...

[1] https://en.wikipedia.org/wiki/List_of_most_massive_black_hol...