Basically all of them? Thermal and nuclear are not clean energy and rely on mining (unless you mean geothermal), and wind has its issues with regards to wildlife and rural living. Rather than seeking a general optimal form of energy production, we should seek rational and deliberate allocation depending on the geographical and social conditions.

I think nuclear is the best

Depends on the geography.

The birds will have something to say about us harvesting all that wing energy. ;)