Judas was given six chances, four of which come at the Last Supper. Jesus, in His great Mercy knows the heart of sinners and calls all sinners to repentance. Some sinners, like St. Peter repent and convert, others like Judas despair of God's Mercy, turn in upon themselves and refuse to change. Jesus is the Good Shepherd forever seeking out the lost sheep, even if that lost sheep is sitting at table with Him.