Q: When Christ uttered "It is finished" did the "Atonement" end at the cross as some Christians claim?
A: No.
---What was finished was the battle--it was one. There was no turning back. Lucifer had Lost. Christ now had the blood of the Lamb Without Blemish, (And ye shall offer that day when ye wave the sheaf an he lamb without blemish of the first year for a burnt offering unto the LORD.-----But with the precious blood of Christ, as of a lamb without blemish and without spot: Lev. 23:12/1 Pet. 1:19) to take to the Sanctuary for the real day of Atonement known as the Judgment.
When Jesus therefore had received the vinegar, He said,
It is finished:
and He bowed His head, and gave up the ghost.
by a greater and more perfect tabernacle,
not made with hands, Neither by the blood of goats and calves, but by His own blood He entered in once into the holy place, having obtained eternal redemption for us.
For Christ is not entered into the holy places made with hands, which are the figures of the true;
but into heaven itself,
now to appear in the presence of God for us:
Nor yet that He should offer Himself often, as the high priest entereth into the holy place every year with blood of others;
For then must He often have suffered since the foundation of the world: but now once in the end of the world hath He appeared to put away sin by the sacrifice of Himself.
(Context that Paul is Describing Here)
And as it is appointed unto men once to die,
but after this the judgment:
So Christ was once offered to bear the sins of many; and unto them that look for him shall he appear the second time without sin unto salvation.
John 19:30/Hebrews 9:11, 12,24-28