Opinions on the beginning...
***SPOILERS***
When Nebula and Tony were alone, drifting in space all of the peril and vulnerability was focused on Tony, Tony was about to run out of air and die. Nebula put him in the pilot's seat. Were they both in peril or was it really just Tony? Did she have a way to live much longer or were they both set to die on that last day? Since she was kind of caring for him after he lost consciousness they almost made it seem like she was going to be ok for some time longer.