Palpatine has his lightsaber (Disney trilogy elements including The Rise of Skywalker will not count because they are not created by Lucas).
Voldemort has the Elder Wand and all seven Horcruxes (but if you want you can disqualify Harry Potter).
Palpatine has no aid from Darth Vader, clone/Stormtrooper army, Darth Maul, Count Dooku, or General Grievous. (Rey does not exist as stated above)
Voldemort has no aid from corrupted Wizards (Harry Potter is a Horcrux and counts as a factor, but as said he can be taken out for sentimental reasons) or from Nagini, as he wishes to keep him away from a fight. Factors from Harry Potter book series are up to you to be included.
The fight zone can be in the courtyard of Hogwarts University or in the Senate courtroom, Death Star II, or a desert, as long as the zone is neutral. No interference from heroes.