I believe FortiToken is the simplest to implement.
Fortinet FortiToken is valued for its quick installation and flexible soft or hard token options, offering cost-effectiveness. Its seamless integration with Fortinet provides robust two-factor authentication, while the mobile app simplifies management with user-friendly features like push-button authentication and OTP reloading. However, it lacks comprehensive reporting and requires FortiAuthenticator for multiple FortiGate integrations. Support for older systems and consistent pricing also needs improvement, with enhancements needed for SMS and hardware solutions.