Qui Gon
I hope he, as a force ghost tries to talk some sense into Vader. I'm still hoping Vader turns good before the events of Return of the Jedi
shareI'm hoping that he will conjure up some physical plane fire from his ethereal no man's land - as the master Star Wars filmmaker Riian Johnson showed was possible - and properly burn Anakin to death before the events of the OT have even started.
That would fix the plot hole of why that Jedi ghost super power had never been used before...