Out Of Every Bending Style In Avatar: The Last Airbender, This One Stands Above The Rest
"Avatar: The Last Airbender" blends east Asian concepts of chi and energy work with the traditional four western elements: earth, air, water, and fire. In the world of "Avatar," some people have access to elemental powers and can "bend" one certain element. One person, the Avatar, can control all four elements.
Earthbenders can mess with rocks and dirt, and later, metal and magma. Airbenders manipulate air in all its forms, including the air in enemies' lungs, should they feel like it. Waterbenders can manipulate water as a solid, liquid, and gas and they can also bend the water inside of things. Finally, firebenders create fire (and sometimes lightning) from their chi.
"A:TLA"'s sequel series, "The Legend of Korra" also explored energybending, when a bender warps a living thing's very life force. "The Legend of Korra" also explored more of the ways each bending style could be made more deadly. Viewers got an airbender who sucked the life out of the Earth Queen, metalbending cops, and a fascist earthbending mech. However, one bending technique still hasn't lived up to its full offensive potential.
Waterbending is only limited by the bender's imagination
Waterbending often appears to be one of the weaker bending styles, as it has a healing component, and many of its fighting techniques look more like a water balloon fight than a martial art. But that doesn't take into consideration how much water is in every living thing. According to the US Geological Survey, a human body is 60% water. Most of that water is in the brain, heart, and lungs. Even humans' bones are almost one-third H2O. The other bending techniques mostly throw stuff at opponents; waterbending can throw you at yourself.
The "A:TLA" episode "The Puppetmaster" introduces Hama, who invented bloodbending. Hama can control people by manipulating the water in their blood, making them dance like puppets on strings. Katara learns bloodbending from Hama, as well as how to extract the water out of plants. This process leaves any plant life in a certain radius completely desiccated.
It's a good thing Hama never put these skills together. In theory, a waterbender could suck the water out of a human, turning them into dessicated husks. They could also stop their blood from moving at all, killing them instantly. Waterbenders could even break every bone in someone's body from the inside out with some well-applied bending. A coldhearted waterbender could also flash-freeze their opponents by turning their blood into ice. Basically, the world of "Avatar" is very, very lucky that the most powerful waterbenders have also been kind.