Sun wants to kill Jack
In a previous episode Sun mentions that there are two men responsible for Jin's death, one of which is her father. She never mentioned the other. I first assumed it was Widmore, but after there interaction it doesn't seem that way. Towards the end of the finale, Jack was saying why he couldn't get them all together to go back, and he said "Sun blames me for Jin's death." Could Sun be plotting something with Widmore against Jack?