Wolf – ok so Acher’s Tshuva may have not been accepted but he did attain atonement. The point I had been trying to make still stands: No Jew is ever beyond hope completely.
So please no more ‘Yimach Shmo’s and suchlike. If Aron was sane then his act was pure evil (and in the time of Chazal with witnesses, Sanhedrin etc. he would be executed). But he’s still a Jew.
He is obligated to perform mitzvos like any Jew.
He can marry a Jewish woman like any Jew.
If he is a Kohen then his sons can serve in the Beis Hamikdosh.
And if he does proper Teshuva – then we are commanded to love him like any Jew.
Everything else is between him and G-d.