No one comment from a rotation that isn't even within the speciality you're considering will ruin your chances. I'm not even sure what the comment really means - you obviously do, but unless your school puts EVERY comment in your dean's letter, I really wouldn't worry about it. The "excellent rotation" part is more important anyway.
And FWIW, people do get involved emotionally in bad outcomes. You're not supposed to... but when you've been coding a kid, and it was a tragic accident to begin with, and the kid has a bad outcome, well, people are often affected. Even if it's not a kid, bad things happen to good people. It's human nature, and that's why there are critical stress debriefings for EMS/ED staff after such events. The police and fire departments use similar debriefings for their staff. If you need to take to someone, do so - don't let it overwhelm you.
So really, I wouldn't worry about the comment.
Just my 2c