If you believe in the atonement, but you do not believe that all men will eventually be saved, you believe in a ‘limited atonement’. Either you limit the atonement to those who of their own ‘free will’ decide that they want salvation, or you limit the atonement to those whom God elected to salvation before the foundation of the world.
In the latter case, there will certainly be some who are saved because God ‘appointed them to salvation’ (Acts 13:48) and therefore they will come to faith in Christ; a multitude no man can number, we are told in Revelation. In this case, the death of Christ on the Cross actually secured for all eternity the salvation of those chosen by God for salvation.
If man’s natural ‘free will’ limits the atonement to those who make the right decision, not only is the salvation of men ultimately up to those who do so, there is also a possibility, no matter how remote, that all men will reject Christ. After all, Christ died to make salvation ‘possible’ for those who choose rightly, but didn’t actually secure the salvation of any!
I ask you “Which of the above scenarios potentially limits the atonement to the greatest extent?”
I leave the answer to you. Just think about it.