Hello, if I have Doubling Season and Elesh Norn, Mother of machines in play and I cast Vraska, Betrayal's Sting. With how many loyalty counter's does she ETB ?
Both Compleated and Doubling Season's ability are replacement effects and not triggers, so Elesh Norn doesn't affect them at all.
As for the interaction between Compleated and Doubling Season, you get to choose to apply the counter reduction from Compleated before or after the counter doubling from Doubling Season.
(While Compleated might look like a self-replacement effect, which would have to be applied first, it's actually because it modifies how the planeswalker enters the battlefield, not how the spell resolves.)
This means that Vraska will enter with either 6*2=12 if you didn't pay life or your choice of (6*2)-2=10 or (6-2)*2=8 counters depending on if you payed life for her phyrexian mana.