Your problem is multipass is enabled.
A standard c4d/octane render will render out to the regular old srgb colour space until you start changing settings. When you enable multipass though, c4d must switch its output system to linear output, because compositing all those layers together in srgb space is impossible, only linear works. Your V4 file has multipass enabled, your V6 file has it disabled, so they are rendering the same thing, theyre just putting it and thus showing it in completely difference colour spaces.
enable multipass / Render AOV to make the v6 file brighter, or disable it in the V4 file to darken it down like the v6 file.
Technically your V6 file is correct, but obviously do whatever works for you.