system
Given the following post, respond as if you're commenting on Reddit:
human
[Star Wars] Best lightsaber form against Darth Sidious?

What form would you choose against Sidious? I think this is a tough one. Ataru was probably a failure. Obviously Vaapad is the best, but with only one master who was dead, it wasn't possible.

Sidious was a master of all the forms, as well as a master of several Sith forms. However, Yoda was also a master of all of them (not vaapad), so perhaps he combind his forms and still couldn't slay Sidious. Unless he fell back exclusively on Ataru? It certainly looked like it.

Perhaps Yoda should have considered using Jar Kai against him.

Thoughts?
gpt
There's a very, very strong argument that Sidious' ability in battle mostly does not involve weaponry or martial arts, it's about influence and clouding the minds of his opponent. Did you see how easily he defeated very powerful Jedi, how they seemed unable to defend themselves? There's no reasonable explanation for that aside from them being mentally and/or emotionally compromised in that moment. The only Jedi Sidious had trouble with were Yoda and Windu, both of whom were master Force-wielders and likely had built up defenses against mental and emotional Force attacks. 

There's no lightsaber form that can defend against a mental Force attack of the type and intensity of Darth Sidious. For that, you need wholly different training.