I believe FortiToken is the simplest to implement.
Fortinet FortiToken offers ease of installation and rapid deployment with excellent two-factor security integration. It provides flexibility through soft and hard token options and supports multiple authentication methods with a mobile app. Praised for cost-effectiveness, especially in price-sensitive markets, it enhances security with automatic OTP reloading. However, it requires coupling with FortiAuthenticator and struggles with limited reporting, unpredictable pricing, slow support in regions like Bangladesh, and lacks centralized integration, impacting scalability.