Tzadik Tamim

 Noam Elimelech (Noach 3:1) A perfect tzadik was he in his generation The tzadik by the  holy deeds that he does brings G-d into to the world and thus is benefitting his generation since the Shechinah is with them because of his actions. Thus when the tzadik reaches high spiritual levels he causes the connection with G-d and His influence in all worlds. Thus the meaning is that such a tzadik benefits his generation  through his spirituality as well as elevating himself  and even influences the higher realms as expressed by saying that he walked with G-d

Michtav M’Eliyahu (2:184) A tzadik decrees and G-d fulfills – It is obviously true that this does not mean that a tzadik can decree something which G-d doesn’t want. The explanation is that there are tzadikim for whom the whole world exists in their merit. That all that happens in the world is merely a means for us to learn from the conduct of these tzadikim how to elevate our service of G-d. What we learn from them is what preserves all of us from the lowest to the highest. That is what it means that because of their merit we live because we are mere utensils for the tzadik which enables us to see G-d’s great kindness in that He freely sustains the entire world .So when a tzadik who is at this exalted level sees an issue which hides an aspect of G-d’s honor it is appropriate for him to ask G-d to withhold it even if it involves a change in G-d’s normal actions. This is what is meant by “a tzadik decrees and G-d fulfills