I have a 2015 ford flex sel fwd and the back drivers side tire is wearing horribly on just the outside edge. all other tires are wearing normally, but this one is almost to the belt while there is still 1/4" of tread on the rest of the tire. What may it be?

 

Not knowing if any damage was done to the vehicle, your best bet is to have an alignment shop check it out. If all that is required is to correct an alignment problem , that might be all that is required. On the other hand, if there are any worn or damaged parts , they would let you know and you could go from there. Be aware, most shops will not attempt an alignment with badly worn tires. You may be required to have the tire replaced before any alignment is attempted.