Here are some coins that have been criticized or have had issues in the past:
1. BitConnect (BCC) - shut down in 2018 due to Ponzi scheme allegations
2. OneCoin (ONE) - considered a Ponzi scheme by many experts
3. Centra (CTR) - shut down by the SEC in 2018 due to fraud allegations
4. Pincoin (PIN) - shut down in 2018 due to Ponzi scheme allegations
5. Modern Money Team (MMT) - considered a Ponzi scheme by many experts
Please remember:
- Never invest in a coin without researching its underlying technology, team, and community.
- Be cautious of coins with unrealistic promises or guaranteed returns.
- Always prioritize risk management and diversification in your investment portfolio.
Stay safe, and happy investing!