We don't know yet. I doubt everyone will have a tragic ending, but I won't be surprised if there will be some. Especially for example if we don't decide to help Riona or don't support M&J if we're not on their path.
It's definitely going to be Quinn, and it's definitely going to be MJ, either because of the balance or because their relationship will fall apart without you. Jill might be in danger because of the company she started, if she finds out something she shouldn't, and that could put Bella and possibly Sage in danger (given how close they are becoming). Sage might go downhill without you as an anchor after Stefan's accusation. It's not clear yet, but it's possible that others have some connections that could ruin them without you. For sure, DIK's will fall apart if they don't make the right choices or if they don't have a girlfriend. They might face consequences for their drug use, just like most of the HOT's, and there's also prostitution involved. The end doesn't have to be fatal. Some of the girls might become depressed without your support, and their lives might start to deteriorate. There are many possibilities. But with this first game, I'm now worried about everyone.
What I'm absolutely certain of now is that we won't be able to save everyone, and someone is bound to end up in trouble. We have more than 10 people with whom we can build relationships. And don't forget about the ending where the mansion catches fire at a graduation party or any other event, and everyone burns to death.