So how is a said, non-existent being, God, supposed to be the greatest source of evil?

[The Fury]

Screamapillar said:

The Fury said:
If God exists, why does he let many suffer so?

Because people have free will, and are allowed to make choices, whether they are good or poor choices.  People are also a product of their environment.

Yeah, because sometimes it's a choice to live in a earthquake/tsunami zone or get cancer. Free will is great like that.