Answer:
Male Platypuses have ankle spurs on their hind legs through which they can dispense venom composed largely of defensin-like proteins (DLPs), unique to the Platypus. This venom is powerful enough to kill smaller animals, and to cause agonising pain to humans.
Platypuses also dig burrows into riverbanks. These burrows are only large enough for smaller predators to enter, but they do not provide protection from snakes.