system
Given the following post, respond as if you're commenting on Reddit:
human
[Revenge of the Sith] Why does Palpatine continue to shoot force lightning at Mace Windu, even after Windu deflects it back at Palpatine?
gpt
No Jedi alive has really contended with Force Lightning. Certainly not to the extent of successfully countering it. So seeing Windu blocking it *barely* suggests that Windu can be overpowered by it. It's evident too, as Windu screams that he's unable to hold it back. As Palpatine *definitely* isn't short on Force Lightning, he feels he can overpower Mace eventually. As an added bonus, he needs to seem like he's extremely powerful *but* at severe risk of dying. Why? Two reasons.

Firstly, he needs Mace to still question whether Palpatine should be left alive or not. If he gives up immediately and Windu can sense that it's a charade (as he's still *bursting* full of Force energy), he might straight up kill him. If he overdoes it, Windu might find an opening and kill Palpatine in self-defence.

Secondly (and most importantly), Palpatine *needs* Anakin to see his vast power *but also* that he is using it out of desperation, that he's about to die at Windu's hand and take all his Sith knowledge of how to prevent death (like Padme's) with him to the grave. He needs Anakin to realise how critical things are and that it won't be resolved through discussion. To bolster this, if he keeps attacking Mace, Mace is more likely to react aggressively and tell Anakin Palpatine needs to die. This would prompt Anakin to intervene, just as Palpatine predicted.