There are several cryptocurrencies that have been deemed fraudulent in recent years. Here are some well-known examples:

1. **BitConnect**: It was considered one of the biggest fraudulent schemes, promising huge returns, but eventually went bankrupt in 2018.

2. **OneCoin**: It claimed to be a cryptocurrency, but was actually a Ponzi scheme, resulting in huge losses for investors.

3. **PlusToken**: It was a cryptocurrency wallet that promised high rewards, but ended up being shut down and stealing billions of dollars in investors’ money.

4. **WoToken**: It was considered another version of PlusToken, which misused funds and collected billions of dollars in investments.

5. **Centra Tech**: It claimed to offer a crypto-enabled credit card, but was subjected to legal action and shut down.

### Tips to avoid fraud:

- Check for reliable staff and clear information.

- Look for reviews from other investors.

- Avoid promises of unrealistic returns or pressure to buy quickly.

Always make sure to do thorough research before investing in any cryptocurrency.