Sorry-noticed another thread. http://mugenguild.com/forum/topics/sonic-and-shadow-abab-updated-041810-110217.0.html .
The characters were not made by me. All of them were made by ABAB.
Go to this site to see the characters, and note, the site is in Japanese... Of course, that's obvious since both characters have a Japanese sound pack. The author is mainly making touhou edits/other characters anyway.
Another thing is that Sonic has an alternate form. Knuckles does too. You can access it by holding START and pushing any of the keys when you are on the character select screen.
Spoiler, click to toggle visibilty
Anyone can have their opinion about these characters, but I think they are beatable. Even though they're hard to beat...
Please give feedback if it's necessary.