Commenting on the use of “many” with respect to the scope of Christ’s atoning sacrifice, and how it is evidence of unlimited, not limited or particular atonement, Ken Hemphill wrote the following:
Many. The word “many” is used twice in Matthew’s Gospel in reference to the atonement of Christ. Jesus said, “the Son of Man did not come to be served, but to serve, and to give His life a ransom for many” (20:28). He alone fulfilled the role of God’s Servant as described in Isaiah 52:13-53:12. The phrase “to give His life a ransom for many” is one of the clearest statements of the atoning effect of Jesus’ death. The Greek term translated “ransom” is used only here and in the parallel passage, Mark 10:45. However, a term built on the same Greek root is used by Paul in 1 Timothy 2:6, “who gave Himself as a ransom for all” (italics mine) . . . Many comes directly from Isaiah 53:11 and will be repeated again in Matthew 26:28 in a context indicating Jesus’ vicarious suffering. As Jesus celebrated the Passover with His disciples, He referred to His blood being poured out for forgiveness of sin, clearly echoing sacrificial language and indicating the atoning nature of His approaching death. R.T. France notes, “At Qumran and in some Rabbinic writings ‘the many’ is a term for the covenant community, derived probably from the use of the word in Isaiah 53:11-12 and Daniel 12:2-3, 10” (R.T. France, Matthew in Tyndale New Testament Commentaries [Grand Rapids, MI: Eerdmans Publishing, 1985], 294). Thus, Jesus was not restricting the extent of the atonement but was simply identifying His ministry with the Suffering Servant.
“Many” here does not contradict “all” of 1 Timothy 2:6. The Suffering Servant gave Himself as a sacrifice to create a new covenant community made up of all who trust in Him.
One of the most significant passages for the use of “many” in regard to the atonement is found in Romans 5:12-19 . . . For our purposes it is important that we note the alternation between “the many” and “all” throughout this section.
“Therefore,” which begins the section, regards back to the affirmation that Christ died for the ungodly (v. 6), which enabled sinful humans to be reconciled to God (v. 10). Paul began by indicating the impact of the sin of the one man by which death spread “to all men, because all sinned” (v. 12). It is not simply that humans are sinners by birth; we are sinners by choice. Paul returned to this thought in verse 15, but this time he used the phrase “the many died,” balancing it with the grace of God, which abounds to “the many.” As in Matthew, “many" echoes Isaiah 53:11, identifying Jesus with the Suffering Servant.
Paul concluded, “So then as through one transgression there resulted condemnation to all men, even so through one act of righteousness there resulted justification of life to all men” (Rom. 5:18). Paul was affirming that Christ’s death was more powerful and efficacious than was the sin of Adam and was sufficient for “all men,” because it actually atoned for the sins of all people.
In Hebrews 9:23-28 the author contrasted the priesthood of Jesus with that of the Old Testament priests. Christ did not enter a holy place made of human hands, but He appeared in the presence of God to put away sin by the sacrifice of Himself. “So Christ also, having been offered once to bear the sins of many, will appear a second time for salvation without reference to sin, to those who eagerly await Him” (v. 28). The language of this section again echoes Isaiah 53:12. “He Himself bore the sin of many,” and also verse 10, “He would render Himself as a guilt offering.” The author anticipated Christ’s reappearing when He will bring the blessings He won during His first appearance for “those who eagerly await Him.” Here, again, “many” refers to all those who have responded to His sin offering and therefore eagerly await His return. (Ken Hemphill, Unlimited: God's Love, Atonement, and Mission [Traveler’s Rest, S.C.: Auxano Press, 2018], 61-63)
For more articles refuting Limited Atonement, see, for e.g.:
Refuting Jeff Durbin on Mormonism and the Atonement (discusses 1 John 2:1-2; Heb 2:17; 10:10-14)