► What is this open-source fighting game called M.U.G.E.N?
https://en.wikipedia.org/wiki/M.U.G.E.N

► You can download the stock game here:
http://network.mugenguild.com/justnopoint/mugen100.zip

(There should be all kinds of tutorials on the web of how to set it up, import characters, etc.)

► YouTube Demonstration Channel:
https://www.youtube.com/channel/UCyHbaJSAmv28Ru9iwH4jSKQ

► Disclaimer:

(All characters and music belong to their original owners. I do not claim ownership of any character used, as this is just a game engine in which people create/code characters to battle. No infringement of any kind is intended.)