League of Assassins; I guess refering to the group in Arrow show of the Arrowverse.

currently unsure whether or not any of movie's makers watched any of those episodes. also currently unsure on any intentional similarity with any non-MCU franchise.

They were in Arrow, but I’m just referring to the league as a whole, mainly referring to them in the comics. They appear in animation and the Dark Knight trilogy too. And I’m not just referring to the Ten Rings in the film, but in the comics too.

I just looked it up and as it turns out the Mandarin was created way before Ra's al Ghul was but the Ten Rings organisation was probably intended to be the MCU version of the League of Shadows (it's a better name for a secret assassin group rather than just stating it) because Marvel loves eating DC's lunch before they order it

I mean both groups compared to the other so I don’t think they are a ripoff but it has been a while since I watched Arrow so I will have to watch it again

about comics; have not read any of those.

though from searching internet, organization version of Ten Rings seems to be just MCU. comic version of Ten Rings; seemingly just literal rings.

currently unsure how many of the makers read comics and also unsure on the specific comics each comic reader would have read before then.