I dont like hurting animals but these dumb beasts only have one real weapon which is in their legs. My core is pretty strong so im sure i could eat both of their feet to my stomach and close the distance on them before i was disabled. Kangaroos rarely take punches to their head that travel at speeds exceeding the speed limit for automobiles. Once you connect a right cross to the jaw of a kangaroo im sure it will become passive and concede to the fact that the afterlife is approaching. Im honestly pretty sure i could beat a kangaroo to death if it pissed me off.
A full-size male red Kangaroo would be taller than you (at their tallest, 6.5 feet,) weigh more than you (up to 250 lbs) and one kick would be able to shatter some of your ribs and/or cause internal damage.
Their punches aren't weak, either. There are many people who have been KOd with one punch from a full-size kangaroo.
They also have claws that can cause serious bleeding damage and sever the femoral artery (this actually almost happened to an uncle of mine once when he was in Australia... he still has a crazy scar.)