Wherefore, as by one man sin entered into the world, and death by sin; and so death passed upon all men, for that all have sinned . . . .  But not as the offense, so also is the free gift. For if through the offense of one many be dead, much more the grace of God, and the gift by grace, which is by one Man, Jesus Christ, hath abounded unto many.  And not as it was by one that sinned, so is the gift: for the judgment was by one to condemnation, but the free gift is of many offenses unto justification.  For if by one man's offense death reigned by one; much more they which receive abundance of grace and of the gift of righteousness shall reign in life by One, Jesus Christ.  Therefore as by the offense of one judgment came upon all men to condemnation; even so by the righteousness of one the free gift came upon all men unto justification of life.  For as by one man's disobedience many were made sinners, so by the obedience of one shall many be made righteous (Rom. 5:12, 15-19).
This passage uses the literary form of a simile to compare the results of the action of Adam, to the results of the action of Jesus. Notice the Apostle Paul used the "as / so" combination five times in just these six verses. Paul also compared Adam to Jesus in 1 Corinthians 15:45, where he wrote, "And so it is written, The first man Adam was made a living soul; the last Adam [was made] ("Was made" was not in the original text, but was added by the translators - If anything needs to be added "for clarity," I believe the word "is" would be consistent with the teachings of the rest of Scripture) a quickening spirit."
Verses twelve and eighteen use the word "all" in reference to scope of Adam's sin and Christ's sacrifice, but verses fifteen, sixteen, and nineteen use the word "many." These two words are not interchangeable. While "many" may, on occasion, be quite close to "all," it is never equal to 100%. "All" is always 100%. Therefore, there must be a reason Paul used both πᾶς (all) and πολύς (many).
ADAM - ALL: All who sin die spiritually (Gen. 2:17; Jn. 3:3-9; Jn. 8:24).
ADAM - MANY: Exceptions to all: the unborn, the new born, and Jesus.
JESUS - ALL: He died for the sins of the whole world (Jn. 3:16; 2 Pet. 3:9; 1 Jn. 2:2).
JESUS - MANY: Exceptions to all: (Joel 2:32; Ps. 86:5; Jn. 1:11-12; Rom. 10:13).
If you want to be one of "His many," receive His gift offered to "all!"