Gaara had it the worst. Nagato should have been able to grow up to understand what really happened at his house. It was an accident caused by his own parents. The shinobi were even regretful afterwards.
Sasuke's initial trauma was between those two things in intensity, but he chose to give up on Team 7 to pursue his revenge. He didn't need to give up on them to get stronger, but he decided to anyway. So, you can't file that under his team being taken away from him. They actively tried to get him back.
Nagato had to live with having seen his parents murdered in front of him regardless of what the reasons were. That trauma isn't going to disappear. He then had to deal with near starvation on a constant basis, downright horrible weather, and as we saw in his flashbacks living right on the edge of a battlefield where death was a constant presence. His team/family then being taken from him later, after he'd decided to do everything he could to protect him, would've just been icing on top of a crappy life cake.
I wasn't saying Sasuke had his team taken away from him. I'm saying that he was similar to Nagato in that he found a team that became like his family.
I again don't think there's any way to say who had it the worst, or that it's even appropriate to compare. They all had it bad and had credible reasons for turning out the way they did, unlike Obito. His was the one thing in this story that I can say was an overreaction to what happened to him, based on the situation itself and his status within the story.
I can't force you to believe me that's your choice. People live their lives bound by what they accept as correct and true. That's how they define "reality". But what does it mean to be "correct" and "true?" Merely vague concepts...their reality may all be a mirage. Can we consider them to simply be living in their own world, shaped by their beliefs?-Itachi Uchiha