From the article Shocking Beliefs of John Calvin:

7. Calvin believed that God did not create all humans on equal terms, but created some individuals for eternal damnation.

This idea is known as “double predestination.” According to this view, God predestines some to salvation and others to destruction. While this idea will not be shocking to some Christians, particularly Calvinists, the idea that God would knowing create some individuals so as to destroy them eternally in the end is shocking to many believers.

According to Calvin, “The predestination by which God adopts some to the hope of life, and adjudges others to eternal death, no man who would be thought pious ventures simply to deny . . . By predestination we mean the eternal decree of God, by which he determined with himself whatever he wished to happen with regard to every man. All are not created on equal terms, but some are preordained to eternal life, others to eternal damnation; and, accordingly, as each has been created for one or other of these ends, we say that he has been predestinated to life or to death.” [16]
Chapter 21 of Book III of John Calvin’s Institutes of the Christian Religion is called “Of the eternal election, by which God has predestinated some to salvation, and others to destruction.”