Kangaroos are powerful kickers

Males will often fight each other for dominance or win a mate. Balancing on their tail, they lean back and punch and kick out, trying to knock their opponent off balance. They sometimes wrestle too. Big claws on their feet and huge muscles in their legs ensure that the kick is painful and damaging. Male kangaroos have thickened skin around their bellies to protect themselves from these powerful kicks. 

Male kangaroos learn to fight by training when they are young. At first with their mum and later with other young males.