First, he’s forcing her to remember painful memories. Those feelings are also ones that will alienate her from her parents, destabilizing the group and her role as leader.
And a side effect of that alienation from her parents is that it plants seeds of doubt in their minds, as well as emotionally crippling Emma herself. It’s like 3 for the price of 1.
I think the second set of promotional photos and taglines adds credence to this idea- as they several are regarding believing a (insert the dark or sad side of a character here) can overcome their personal demons, demons that Pan is going to do his best to use.
In the end, I think we’ll have a situation where many of the characters don’t believe in themselves and are consumed by self doubt- but unlike the beginning of the season, they will start to believe in one another. This unity will be the weapon they use to defeat Pan, who will likely have expected them to crumble.
I could see that happening, with them ultimately starting to believe in each other and work together more effectively. One of my big questions right now though is what does Pan actually hope to achieve with this lot? Sure, he’s broken down plenty of people before, but as far as we know they’ve all been random kids. This time we’re talking about the destined kid in the picture and his family, this is the culmination of a game that started centuries earlier, so I’d think that the stakes would be higher in this case, and perhaps the objective is even different to what Pan’s done before?