People: "If God, then why bad?"[0]
Leibniz: "God and bad can coexist. E.g. we live in the best possible world."[1]
Voltaire: "Here's a depiction of some fictional bad."
I don't think Voltaire engaged meaningfully with Leibniz's argument. (I think that Leibniz is simply right tho, in the mathematical sense, so there isn't much room for Voltaire anyway.)
Doesn't Leibniz's argument assume a single all-powerful god, and an external notion of good and evil? I would call it a 'not-even-wrong' argument - perhaps it's perfectly correct given its assumptions, but the assumptions aren't (necessarily) anything to do with this world...
[0] : https://en.wikipedia.org/wiki/Problem_of_evil
[1] : https://en.wikipedia.org/wiki/Best_of_all_possible_worlds