The cleanest and best bang for the buck if you don't have to spend years fighting eco-nuts, is nuclear. Long lasting, clean, low risk in both implementation and operation. Storing spent fuel rods is less impactful on the landscape and the environment than discarded wind turbines and defunct solar panels.
Hydro would be up there very close to number 1 with me, but it's not something you can build anywhere. Nuclear does require a water source for cooling but that source can be much smaller than what is required for efficient large-scale hydro. Again you have to fight the eco-nuts.
They don't seem to care if the pollution is out of sight and if it requires dangerous mining often done by slave and child labor OR that it gives the advantage to those who control the materials needed, to our enemies.