I've read the original document (link on the right of the page) because news outlets often don't put the whole story. It turns out he's not been sued only for fraud. I've summed up every claim below. For the full claims, see the original document. The number of claims in the title is regarding this last filing.

The Defendants are Do Kwon himself and Terraform Labs.

FIRST CLAIM: Fraud in the Offer of Sale of Securities

Defendants, in the offer or sale of securities, knowingly or recklessly: employed devices, schemes, or artifices to defraud; obtained money or property by means of untrue statements; engaged in transactions, practices or courses of business which operated or would operate as a fraud [...].

SECOND CLAIM: Fraud in Connection with the Purchase or Sale of Securities

The same as the first claim.

THIRD CLAIM: Control Person Liability

Kwon is, or was, directly or indirectly, a control person of Terraform. As such, he is jointly and severally liable with and to the same extent as Terraform Labs itself for its violations of the Exchange Act.

FOURTH CLAIM: Unregistered Offers and Sales of Securities

Defendants, directly and indirectly, without a registration statement in effect as to that security, sold securities.

Here, they are referring to the things that Terraform sold: UST, LUNA, mAssets and MIR. The last two are, respectively, a mirrored version of regular stocks and the tokens used to trade these.

FIFTH CLAIM: Unregistered Offer of Security-Based Swaps with Non-Eligible Contract Participants

Defendants made use of means of transportation or communication to offer to sell, offer to buy, or purchase or sell a security-based swap to persons that are not eligible contract participants. The securities were not registered with the SEC either.

SIXTH CLAIM: Effecting Transactions in Security-Based Swaps with Non-Eligible Contract Participants

Defendants effected transactions in security-based swaps with or for a person that is a non-eligible contract participant, without such transaction being effected on a national exchange.

Non-eligible contract participants are, basically, retail investors

The CFTC defines Eligible Contract Participants as follows:

Eligible Contract Participant: An entity, such as a financial institution, insurance company, or commodity pool, that is classified by the Commodity Exchange Act as an eligible contract participant based upon its regulated status or amount of assets. This classification permits these persons to engage in transactions (such as trading on a derivatives transaction execution facility) not generally available to non-eligible contract participants, i.e., retail customers.

Other aspects

• Defendants misled customers to believe that Chai, an Asian version of PayPal, was using their blockchain to settle payments. This was not true: they simply recorded the transactions on the blockchain to make people believe they were happening there;
• The first de-peg (May 2021) was avoided by a third-party buying huge sums of UST. Do Kwon claimed that it was avoided by the superior algorithm they had, and never mentioned this third party;
• $40bn were lost;
• About the jurisdiction, the SEC claims some of the misconducts happened either in US soil or with US people involved, therefore they have the right to sue the Defendants;
• Articles 23 and 24 basically classify almost every token as a security;

TL;DR

Do Kwon and Terraform Labs traded tokens classified by the sec as securities without being registered on a National Exchange. They also willingly defrauded customers, according to the SEC filing.

That's it, folks!