Don't ever force close actual PC games like that, there is a very good reason nearly every game warns you not to close or turn off your PC while it is saving, you risk corrupting your save data by just closing a program in that way. Use the games own menu to exit PC games. If a game doesn't have that option, which honestly i don't think i have ever seen one, then as you say its probably ALT-F4, but that is already a combo we use, when you have "close active window" setup in Bigbox, we first send ESCAPE, if that doesnt work, then we send ALT-F4.