"juega vivo" is actually two words. I don't think "opportunistic" is quite strong enough as the word "juega vivo" often carries a far more negative connotation, and bordering on the illegal.

https://www.italaw.com/sites/default/files/case-documents/it...
See page 192:
913 See Pérez ¶ 8 (describing Panama’s juega vivo culture of “exploiting every angle and gaining every
advantage”); id. ¶ 53 (stating that it is “not unreasonable or farfetched that Mr. Varela would have asked Mr. Rivera” for a $600,000 campaign contribution”).

page 246:
1162 See Pérez ¶ 53 (explaining that not engaging in good faith with contractual partners by “delaying, obfuscating
and manipulating negotiations” is consistent with the practice of “juega vivo”).


¿Qué es argolla en Perú?
Goal: En el Perú –y en otras partes de América Latina- se suele llamar argollas a grupos cerrados de personas que monopolizan o regulan el acceso a determinados beneficios, oportunidades o formas de poder y prestigio, apelando a ciertos lazos comunes de afinidad y excluyendo a otras personas ajenas a esos círculos.

https://forum.wordreference.com/threads/argolla-peruanismo.1...
Entiendo que significa, formar grupos de personas que se vinculan como si estuvieran en una "hermandad", y que manejan y favorecen según sus caprichos y antojos a otras personas (miembros o no miembros de su "argolla") en cualquier entorno o sociedades. Es algo muy similar a lo que sucede con los estudiantes de Universidades de USA que suelen agruparse en "hermandades" con nombres ideados por ellos mismos. This link makes reference to another word "camarilla" used in other Latin American countries.

Camarilla is borrowed from Spanish and is the diminutive of "cámara," which traces to the Late Latin camera and means "room"; a "camarilla," then, is literally a "small room." Political cliques and plotters are likely to meet in small rooms (generally with the door closed) as they hatch their schemes, and, by 1834, "

https://www.dictionary.com/browse/camarilla
a group of unofficial or private advisers to a person of authority, especially a group much given to intrigues and secret plots; cabal; clique.

Just a few ideas/options but time does not allow me to research further.

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Note added at 1 hr (2021-09-15 17:48:38 GMT)
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https://www.liveincostarica.com/blog/2014/01/what-is-an-argo...
However, in Costa Rica this term has a completely different connotation. Here it refers to a closed group of insiders or clique.

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Note added at 4 hrs (2021-09-15 19:54:03 GMT)
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Andre:

I really don't know why you would be looking for an "idiom" or "idiomatic phrase" when what you have are a set of words!

"Compadrazgo", "el juega vivo", "la argolla", "la coima", etc., unless the text you have provided is only indicative and not the actual text being translated? I have to say I am not happy with "corrupt clique" either as I am sure there is "one word" that can be found to describe "argolla".

As far as "juega vivo" again it appears to be a word or phrase that you need as opposed to something idiomatic, but ... ?????????

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Note added at 6 hrs (2021-09-15 22:01:07 GMT)
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I read the www.quora.com entry, and if one word does not suffice, a phrase caught my eye ... “Juega vivo” covers a broad range of situations from exploitation of every angle to gain an advantage, to an outright swindle. In other words, one option is to maintain the Spanish term then offer an explanation, or use a footnote.

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Note added at 6 hrs (2021-09-15 22:08:59 GMT)
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Synonyms:
Definitions from Oxford Languages
cabal > a secret political clique or faction.
"a cabal of dissidents"

Similar:
clique
faction
coterie
band
gang
cell
sect
caucus
junta
pressure group
camarilla


ARCHAIC
a secret intrigue.

There was a high (40%) victimization rate in Perù, which has decreased in recent years. A former president of Perù was convicted of abuse of power, corruption and money laundering before he fled to Japan in 2006 (according to Wikipedia). Perù was known for its production and illegal trading of drugs.
Travel guides used to warn people of the risks for tourists in Perù, who could be targets for criminal networks or gang rings. Travel guides also advised people to make health care provisions in case of travel sickness or infections.