Kudo causes all creatures to have base power and toughness 2/2.
Because Elesh Norn gives creatures your opponents control -2/-2, they will be 0/0 creatures and die as a state-based action due to having zero toughness.
This is also true for any creature that enters the battlefield under an opponent's control.
Results
Destroy all creatures opponents control.
Destroy all creatures that enter the battlefield under an opponent's control.