God redeemed mankind in the Age of Grace, so why does He still need to do His work of judgment in the last days?

Bible Verses for Reference:

“You shall therefore be holy, for I am holy”(Lev 11:45).
“Holiness, without which no man shall see the Lord” (Heb 12:14).

“And if any man hear my words, and believe not, I judge him not: for I came not to judge the world, but to save the world. He that rejects me, and receives not my words, has one that judges him: the word that I have spoken, the same shall judge him in the last day” (Jhn 12:47-48).