The ending is a slight cheer up; they manage to find Dan within Pandora's box, and they try to get him out.
Ryu and Ken's ending has Pandora's Box causing Ryu to vanish. Whether he's dead or not is unconfirmed, but seeing Ken holding his headband with the thought that his lifelong brother figure might be dead is really heartbreaking.
Jin and Xiaoyu's ending has Jin's Devil Gene reacting to the Pandora's Box and vanishes similarly to Ryu while Xiaoyu repeatedly and helpless calls out Jin's name. Xiaoyu looked visibly devastated during and after this disappearance...
If you thought Christie couldn't already catch a break in Tekken, she's not exempt from Tear Jerkers even in crossovers. In the third Vita episode; Christie sees through a soundproof glass Eddy getting shot and presumably blown up by a grenade.