Palpatine managed to infiltrate the government of the galaxy, utterly corrupt it, and cause the government to basically hand him all his power on a silver platter, all while keeping everyone in the dark about his true identity and motives. Voldemort is an absolute chump compared to Palpatine.
Well there is a difference, in the case of Voldemort he was fighting a large group of wizards and witches, Palpatine waged war for years and was going to lose until he executed order 66. Also his enemies weren't all Jedi or force users, most of them were just people who couldn't stand a chance against a force user. Voldemort also had a very limited number of followers compared to palpatine. Basically it's more like if Palpatine and a doku took on a group of Jedi all at once in one all out fight.
Uhhhh Palpatine manufactured the war only to get him elected as the chancellor, and he prolonged the war to have emergency powers voted to him basically securing his power over the Senate. He used Anakin to do the dirty work of taking on the entire Jedi temple with his troops. Basically, since he ordered the clones under the guise of a deceased Jedi giving him full control of them, also controlled the Confederation of Independant Starsystems which includes their droid armies, and controlled the Senate of the Republic, literally his only enemies were the Jedi, all of which force wielders. And like I said Anakin did fight a large group of Jedi lol. I'm not saying either Palpatine or Voldemort are stronger than the other, but come in check your facts
He only attacked the school to draw out Harry.