'frozen' app that can't be forced closed

Hey everyone, so I deleted this third-party app (a game which tons of others have downloaded from the web - so it should be safe.) , but after I deleted it, it's still there. When I try to delete it, the system says it's still open, but there's no way to force quit it. (and when I tried to force quit it using Terminal - I can't find the app there at all) - is there anyway to fix this? because I can't shut down the computer with it still running :/

Thanks ~