betray, betrayer

Definition:

The term "betray" means to act in a way that deceives and harms someone. A "betrayer" is a person who betrays a friend who was trusting him.

Judas was "the betrayer" because he told the Jewish leaders how to capture Jesus.
The betrayal by Judas was especially evil because he was an apostle of Jesus who received money in exchange for giving the Jewish leaders information that would result in Jesus' unjust death.

Depending on the context, the term "betray" could be translated as "deceive and cause harm to" or "turn over to the enemy" or "treat treacherously."
The term "betrayer" could be translated as "person who betrays" or "double dealer" or "traitor."

21:11 Other prophets foretold that those who killed the Messiah would gamble for his clothes and he would be betrayed by a friend. The prophet Zechariah foretold that the friend would be paid thirty silver coins as payment for betraying the Messiah.
38:02 After Jesus and the disciples arrived in Jerusalem, Judas went to the Jewish leaders and offered to betray Jesus to them in exchange for money.
38:03 The Jewish leaders, led by the high priest, paid Judas thirty silver coins to betray Jesus.
38:06 Then Jesus said to the disciples, "One of you will betray me." â€¦ Jesus said, "The person to whom I give this piece of bread is the betrayer."
38:13 When he returned the third time, Jesus said, "Wake up! My betrayer is here."
38:14 Then Jesus said, "Judas, do you betray me with a kiss?"
39:08 Meanwhile, Judas, the betrayer, saw that the Jewish leaders had condemned Jesus to die. He became full of sorrow and went away and killed himself.