Just as the Son of Man did not come to be served, but to serve, and to give His life a ransom for many.
1st Timothy 2:5-6 states: “For there is one God, and one mediator also between God and men, the man Christ Jesus, who gave Himself as a ransom for all, the testimony given at the proper time.”
Question: Does “many” imply something less than all?
Answer: Not necessarily, as John Calvin commented at Mark 14:24: “The word many does not mean a part of the world only, but the whole human race: he contrasts many with one, as if to say that he would not be the Redeemer of one man, but would meet death to deliver many of their cursed guilt. No doubt that in speaking to a few Christ wished to make His teaching available to a large number. At the same time we must note that in Luke (saying for you) He addresses the disciples by name and encourages the faithful as individuals to apply the pouring-out of His blood to their benefit. So when we come to the holy table not only should the general idea come to our mind that the world is redeemed by the blood of Christ, but also each should reckon to himself that his own sins are covered.” (Calvin’s New Testament Commentaries, Matthew, Mark and Luke, Vol. III, James and Jude, p.139, emphasis mine)
John Calvin comments on Matthew 20:28: “‘Many’ is used, not for a definite number, but for a large number, in that He sets Himself over against all others. And this is its meaning also in Rom. 5:15, where Paul is not talking of a part of mankind but of the whole human race.” (Calvin’s New Testament Commentaries, A Harmony of the Gospels: Matthew, Mark and Luke, Vol. II, p.277, emphasis mine)
It doesn’t sound like John Calvin believed in a Limited Atonement. In your discussions with Calvinists, you may bring up Calvin’s commentary, but expect the Calvinist to insist that they are not responsible for defending John Calvin on all points, which is fair, but the point is that it’s not just Arminians that disagree with the perspective of a Limited Atonement.