Ozai. He controlled the complete Fire Nation.

Ozai: The entire Fire Nation and most of the Earth Kingdom

Amon: Republic City

Jianzhu: Most of the Earth Kingdom

Long Feng: Ba Sing Se

Ozai wins

I'd say either Long Feng or Ozai have the most political power

I'd pick ozai overall cause he runs the entire fire nation as well as earth kingdom territories AKA the fire nation colonies the earth kingdom like for example .Omashu aka new ozai. he and the fire nation conquer ba sing se and take control from Long Feng

Obviously Ozai, dominates the most powerful, richest and most advanced nation of the four. While Amon and Long Feng only dominate one city, they would be the equivalent of mayors or governors, while Jianzhu is more of an administrator who only affects part of the Earth Kingdom.