Street Fighter II' Champion Edition was a very popular arcade game. So much so that some other companies decided to hack it and then release it as their own version. Worryingly for Capcom, these hacked editions were more popular than the official version in some places. So, Capcom got their legal team to go after the hacked editions and get them removed whilst preventing the hackers from making any more, whilst Capcom's developers set about making a new official version, which was released later on in 1992 -Hyper Fighting.

The main feature of this hack was the increased speed, along with several other changes.

The most messed up Street Fighter hack ever.

Black Belt Edition
Also known as Rainbow Edition, this is one of the more popular hacks.

Red Wave
Yet another hack of Champion Edition.

And another one.