Final answer:
The Cubozoa class of cnidarians, particularly box jellyfish, possess stings toxic enough to be lethal to humans. They use nematocysts to release potent venom, which can paralyze prey and pose a serious threat to humans.
Step-by-step explanation:
Some individuals in the cnidarian class known as Cubozoa have a sting that is toxic enough to kill humans. Cnidarians, including jellyfish, sea anemones, and corals, possess specialized cells called nematocysts which can release a potent toxin to paralyze prey and deter predators. Among the cnidarians, the Cubozoa class, especially the box jellyfish, are notorious for their particularly powerful venom, capable of causing serious harm or even death to humans. It is important to exercise caution when in waters inhabited by these creatures due to the life-threatening stings they can inflict.