Wait do I need to beat everyone in proud или critical to unlock the black point? I mean what if Ты beat Terra, Ventus and Aqua in standard mode and the final episode in proud? will that work?

First, Ты need to defeat everyone's story (including the final episode) in standard mode. Then repeat Terra, Ventus, Aqua and Final Episode story but do it in Proud mode. Tried it and I got the blank point.