Handle crashes/freezes etc better.

I've a number of games that will crash and cause a non recoverable (at least at my level of linux foo) state, causing me to hard power off to reboot.

I don't know if this is something that Proton could do, but if there were an easy way to kill such applications it'd be nice.

Many unity games when run in full screen have such problems when you alt tab them.
other games such as Homeworld Remastered freeze up on exit and eat the mouse cursor.
in such a state attempting to alt tab or command key might show the task bar but won't - for example if I alt tab to an open command prompt window, will not display it.

The report does not name a source file, test, or entry point. Start by reproducing the fullscreen Unity alt-tab or Homeworld Remastered exit freeze described in the issue and determine whether Proton can recover the affected application state. Done would require a clearly defined recovery mechanism and verification against the reported scenarios.