India’s interesting derivatives market has apparently not yet been discussed in this thread. As can be inferred from the image below, the derivatives market is unbelievably large relative to the market for the underlying assets themselves. India can therefore be considered a Mecca for decadent options trading, in the style of Wall Street Bets. India’s regulatory authority (SEBI) recently published a report stating that 91% of retail investors engaging in options trading incur losses.

(Note: The statistics in the image extend to 2023.)
This has not gone unnoticed by Wall Street, and a firm called Jane Street, in particular, has made significant profits in India’s derivatives market. Jane Street’s activities have now come under SEBI’s scrutiny, and SEBI is accusing the company of market manipulation. The way this allegedly illegal market manipulation came to light is quite amusing: Jane Street sued another firm, accusing it of using JS’s trading strategy in the market, which had allegedly been leaked to them by former JS employees. As a result of the lawsuit, this strategy also piqued SEBI’s interest, which then began investigating JS.
What happened next was that SEBI banned JS from trading in the Indian markets due to market manipulation. JS denies this, but it has nevertheless transferred $564 million in assets to SEBI’s escrow account (I’m not entirely sure about the terminology here, so I’m not completely confident about this expression).
So, what exactly was this alleged market manipulation about? According to Jane Street, their trading was merely based on index arbitrage. SEBI, on the other hand, claims that JS manipulated the index price through loss-making trades; these loss-making trades would have affected index-linked options, which JS also traded, to such an extent that the losses incurred from the alleged index manipulation would still have been smaller than the profits from options trading. The unusual relationship between derivatives and underlying asset trading in the Indian markets makes such manipulation possible.

If my ramblings on the subject are too unclear, or alternatively so interesting that you’d like to explore the topic elsewhere, I strongly recommend the video and podcast episode below on the subject, as well as the FT articles, from one of which the above quote was taken.
https://youtu.be/VhqosmgfGR0?si=h4Z5VEfh20v23A4P
https://youtu.be/ZzjfDS7y1aA?si=oDfuvPCGCbU2McPq
https://www.livemint.com/market/stock-market-news/can-sebi-truly-level-the-playing-field-for-retail-traders-11753510440285.html
https://www.ft.com/content/2438489c-0326-4ffb-b58f-e4a2a7f34f0a
https://www.ft.com/content/41c4789a-afa6-462c-a6ea-9704c2ba78a7