Reanimated Madara and Nagato were close in strength at this moment, making it difficult for either to secure a victory in battle.
Madara possessed the Mangekyo, while Nagato had sealing jutsus like the Adamantine Sealing Chains. Madara's reanimated state could lock his health, and Nagato possessed self-healing abilities granted by the Uzumaki bloodline. Madara had infinite chakra in his reanimated state, while Nagato had chakra provided by the eight tailed beasts inside his body. Although Nagato lacked the Rinnegan, he could still use most of the Rinnegan pupil techniques.
As the two fought, their actual strength was not far apart, and instead, signs of Madara being faintly suppressed by Nagato began to appear.
Because of Wang Ming's butterfly effect, Kabuto Yakushi failed to evolve into Serpent Kabuto, so he did not prepare special sacrifices, causing Madara at this time to be summoned only through ordinary Impure World Reincarnation.
The more massive a ninja's chakra reserve was during their lifetime, the more obvious the suppression became when they were summoned through Impure World Reincarnation.
The quality of Impure World Reincarnation mainly depended on the strength of the sacrifice, or rather, the sacrifice's own chakra volume.
For example: during the Konoha Crush Plan, the sacrifice summoned to bring back Hashirama Senju was merely a ninja from the Hidden Sound Village who participated in the Chunin Ninja Exams in Konoha. Therefore, Hashirama Senju's Wood Release: Advent of a World of Flowering Trees produced wood that could not even cover a single rooftop.
On the other hand, ninjas with relatively little chakra during their lifetime experienced an all-around enhancement in strength when reanimated.
Such as: Reanimated Itachi.
Itachi Uchiha was a renowned combat genius, capable of learning any ninjutsu just by looking at it once. He looked like an exceptional seed for a glass-cannon