I think you and I agree that no one dies in a state of perfect sinlessness. The Orthodox Church and historical Protestantism teaches that when a Heaven-bound man dies, Christ instantly perfects that man and makes him sinless. This happens in harmony with the man’s free will. What happened to Hitler upon death is the same as what happens to each and every one of us upon death: The resurrected Christ instantly perfects us in harmony with our free will.
Once again, I am always surprised when a Protestant (who comes from a background of no Purgatory or anything like it) has difficulty understanding Christ instantly purifying a man at death. That is of the essence of Protestantism. The Reformers took a strong stand against the idea of post-mortem processes. Thus (for example), when a good Lutheran died, his brethren said, “He is now in Heaven.” They didn’t say, “After a period of post-mortem purification, he will go to Heaven.”
I would paraphrase Revelation 20:4-6:
Believers lived and reigned with Christ from the time of Acts chapter 2 all the way up to the Second Coming. The unbelievers were dead in their sins and did not enjoy the blessedness of being members of the Church. Being baptized, being a member of the Church, is the first resurrection. Blessed and holy are the members of Christ’s Church. Over them spiritual death has no power (unlike the unbelievers who are dead in their sins). The members of the Church are priests of the Holy Trinity, and they shall reign from the time of Acts chapter 2 all the way up to the Second Coming.