Atoned:
--to make amends or reparation, as for an offense or a crime, or for an offender (usually followed by for): to atone for one's sins
If the Christ atoned for everybody's sin w/o exception, then He has amended, repaired their stance before the Father. None in this category will ever taste eternal death.
--to make up, as for errors or deficiencies (usually followed by for): to atone for one's failings.
Seeing that all have sinned and fall short of the glory of God, all are failures. If the Christ atoned for all w/o exception, He has atoned for their failings. When we were this--->For while we were still helpless, at the right time Christ died for the ungodly[Romans 5:6], so if this is applied to everybody w/o exception, then everybody w/o exception has been atoned for, has been reconciled to the Father, has had their failings atoned for.
--to make amends for; expiate: He atoned his sins.
To expiate means to extinguish the guilt incurred by. So, if the Christ atoned for everybody w/o exception, then there is no guilt imputed to them.
--to bring into unity, harmony, concord, etc
So, if the Christ atoned for everybody w/o exception, everybody is united, in a harmonious relationship, in an accord with the Father.
One can not hold to a universal atonement and not also hold to universalism, and remain consistent in their theology.