Rats: Strong normal people that is brought into the employ of Villains. Usually, Rats are employed by the Bigger named villains, like Goliath. They are called Rats because they are the lowest type of scum that exists.
Grunts: Weak superhumans become grunts. The police can still handle them, but if they came in numbers...well let's just hope that doesn't come to pass.
Elites: The Big Villains usually have six elites put in three pairs. Usually, they are number color coordinated. Like let's say one person is assigned the color red and the other a 1. The person that received the color would get a small colored tattoo that looks like this "#". The other will receive a colored tattoo that looks like this "1". That's the most common case. Others are animal brand coded or something that would look good for pairs.
The Left: We're getting into dangerous territory now. This person is The Left Hand of a Big Villain. They are much stronger than the Elites combined. It's also a fought for position. If any of the Elite feel they could take on a Left and they defeat him or her. They could take the position for themselves.
The Right: A Big Villains Right Hand. The second only to the big boss. People who are a Right Hand are not to be messed with. They usually seen stronger than The Left by a big margin. I say usually because there have been accounts of Left's being stronger either because The Big Boss is Left handed or because The Left is strong enough to take the Right's position and title for their own.
The Big Boss: The Strongest of all the baddies. There has never been an account of a Big Boss losing to a Left or a Right. Heck, once an entire group turned on a Big Boss only to be decimated. An near Unrivaled position in the Villain scene. I say near because only Heroes ever fought a Big Boss to a standstill. Though it's only the big names in the Hero side.