Lindsay/Beth
Okay here's my take on it all. You still have feelings for him and you can't have a serious relationship with a man until you work through those feelings or get back with Sean. Sean still has feelings for you and he will sabatoge every relationship he's in until he works through those feelings for you or he gets back with you. Therefore the only logical solution is for both of you to face your feelings head on because if you don't neither of you will ever be happy.