"Now Skywalker... you will die."
Anyone else think the Emperor wasn't going all out at this point in the film? Luke took his lightning for a damn long time.
I still think the Emperor was torturing him at this point in the film... maybe going for long and painful kill? Because realistically a couple seconds of OT Sidious' (probably a step up from ROTS Sids who fried Mace Windu like nothing) lightning should easily kill Luke.