I guess this depends on your definition of power... scientifically power is defined as force times distance divided by time... the faster an object is moved over a given distance the more power that has been used in moving it.
four
the back legs
"Flying Squirrel"
yes
sparrow
Yes
leopards have long and powerful legs to kill their prey,to climb the trees,to run to chase their prey and to kill the enemies.
Squirrel monkeys are agile jumpers and can leap up to 10 feet horizontally from tree to tree. They use their powerful hind legs to propel themselves through the canopy in search of food and to escape predators.
A Flying squirrel
The part of a kangaroo that is very strong is the legs. Their legs are extremely powerful since hopping is their means of locomotion. They can reach speed of 44 miles per hour with those powerful legs.
cheetah
not very strong