Apparently it's meant to be Kylo? At least according to Matt Martin.
https://twitter.com/missingwords/status/1209528928097853442
No clue how that's clear in the comic at all?
But then, the guy's an absolute idiot. I'd say it's far more likely that the comic intended it to be Palpatine or Snoke. And considering we've seen Sheev throwing lightning around in space before and the fact that the voice Kylo hears is, at least according to RoS, Sheev not Snoke; I'm inclined to favor Sheev.