Well, it sounds like views/list.php would be a good starting place. You might even do this without template overrides by using the tribe_events_after_template hook – that way you could “inject” a new list from your theme’s functions.php file, if that happened to be preferable to working with template overrides:
add_action( 'tribe_events_after_template', 'custom_past_events_list' );
function custom_past_events_list() {
if ( ! tribe_is_upcoming() ) return;
$past_list = 'You might call another function which generates this';
echo $past_list;
}
A great deal depends on what you’re comfortable with, but that’s another avenue you could explore.