// Graceful way by process ID
var proc = System.Diagnostics.Process.GetProcessById(9836);
proc.CloseMainWindow();
proc.Close();

// Force kill by process ID
var proc = System.Diagnostics.Process.GetProcessById(9836);
proc.Kill();

// Graceful way by partial window title
var wnd = sp.WindowsFromTitlePartial("Untitled - Paint").First();
wnd.Process.CloseMainWindow();
wnd.Process.Close();

// Force kill by partial window title
var wnd = sp.WindowsFromTitlePartial("Untitled - Paint").First();
wnd.Process.Kill();