In the movie Man of Steel, General Zod is shown as being more powerful than Jor-El, father of Superman.
Why is General Zod more powerful than Jor-El in Man of Steel?
Zod is a soldier with big muscles.
Jor-El is a scientist with smaller muscles.
You'll find, even on Earth, a range of strength levels in individual people.
It seems that in Man of Steel Kryptonians are not born, but "engineered". Every individual is created to fit in a different caste, to cover the needs of Kryptonian society.
General Zod: [Then] join me. Help me save our race. We'll start anew. We'll sever the degenerative bloodlines that led us to this state.
Jor-El: And who will decide which bloodlines survive, Zod?... You?
Meant to be a soldier (and maybe a leader among soldiers) Zod should be better prepared for combat and military tactics than people who fit other roles (such as scientists). As a leader or high rank in the army he has troops under his command, who follow him for his rebellion (If Jor-El has somebody under his command, odds are that they would be scientist or researchers too, maybe even just drones, so his "retinue" could not match Zod's).