An aggressive or mean rabbit is no joke. Rabbit bites can go clear through fingers, bone and all. Rabbit scratches are worse than cat scratches. Some rabbits become so aggressive they will attack any person who enters a room, usually going for the ankles, and will chase, growl, chomp onto lower limbs and not let go. But such behavior is not a reason to get rid of your rabbit.
The first question to ask if you think you may have a mean rabbit is what are you calling aggressive behavior? If a rabbit nips you when you quit petting him or to get you to pay attention to him, this is not really aggressive behavior. It is one of the ways rabbits naturally communicate. Try teaching him not to bite too hard by squealing when his nips are too sharp. If the rabbit bites you or lunges at you when you reach into his cage, this too is acceptable rabbit behavior. The cage is his and he is letting you know that. But if you are talking about attacks, chases, and hard bites with no apparent provocation, you probably do have an aggressive rabbit.
The second question to ask if your rabbit exhibits aggressive behavior is if your rabbit is a young unaltered rabbit. Young rabbits, as they reach sexual maturity, may exhibit more aggressive behavior. This is true of both males and females, and the behavior usually leaves within a month or so after the rabbit is altered.
If your aggressive rabbit has already been spayed or neutered, you probably have a rabbit that was or is being disciplined in an inappropriate manner. Excessively aggressive behavior is usually an expression of excessive fear - the rabbit's fear that he will be hurt. If you raised your rabbit yourself ask yourself the following questions: Do you (or anyone else in your household) try to discipline your rabbit as you would a cat or a dog? Have you struck your rabbit with a newspaper or shouted at it? Do you have young rambunctious children whose behavior might seem threatening to your rabbit? Or a dog or cat whose play may be too rough and frighten your rabbit?
However a rabbit becomes aggressive, the best way to rehabilitate him is with acceptance. Do not compound the problem by trying to punish him for his behavior. Wear long pants, high-topped shoes or boots and gloves if necessary, and meet his aggressive actions with love. Admire him; tell him what a sweet wonderful rabbit he is. It will take time, possibly one or two months, but more than likely the rabbit will gradually respond to this method. As he or she slowly realizes there is nothing to fear from you or his environment, the rabbit will calm down and any charges toward you will be those of welcome.