You can play Mass Effect 2 so bad, you and everyone else gets killed at the end. Not sure what happens when you bring that save to Mass Effect 3.I love that Mass Effect had bad endings. I think it would be better though if it was more like BOTW though.
Do a good job getting everyone to join your team? Great. Easy fight to save the universe.
Do a bad job? Still can save the universe but it is a lot harder.