Benders:
1. Very limited control over your element. You are most likely a young child just discovering your bending skills, or have never attempted to train with them. Not much can be done with this level to harm someone.
2. A year - 2 years of training with your element have made you more adept in your bending. You have the ability to use some sub-elements. You are now a threat to humans, and poorly trained benders. You can hold your own if you need to, however sometimes you may need some back up.
3. Well trained in your element. 3-5 years of training. You have access to more sub-elements, and pose serious threat to anyone. Your presence will not be taken lightly. You can handle large groups of non-benders, or small groups of benders.
4. Dangerous. Years of training and dedication have made you one of the most powerful benders around. Low level benders stand no chance with you, and non benders will have a difficult time, granted they're not trained in chi blocking.
5. Master of element. You are most likely a King or Queen. No single bender stands a chance against you. Even the avatar would have a struggle with you. You are one with your bending. There is no aspect of your power you can not control.
Non-Benders:
1. A regular human. You are most likely a civilian.You stand little chance against a bender.
2. A street fighter. Growing up in a rough neighborhood, or training in martial arts have made you an adequate fighter. You have a shot taking out low level benders.
3. Well trained. You stand threat to benders and non-benders alike. You can hold your own against most opponents. You most likely mastered multiple forms of martial arts.
4. Dangerous. You can go toe to toe with some of the toughest the benders have to offer. You can block chi, and hold your own against a small crowd of benders or a large group of non-benders. You are a force to be reckoned with.
5. Master of combat. You have trained hard to become one of the greatest fighters the world has ever known. When facing a bender of even Master class you pose a threat. You are well disciplined, taught well in the ways of the human body, and can block chi like it's your day job. Look out world.