'Faithless' in the Bible

Judas [also called Thaddaeus] the son of James, and Judas Iscariot, who became a traitor [to the Lord].

Jesus answered, “You unbelieving and perverted generation! How long shall I be with you and put up with you? Bring your son here [to Me].”

Then He said to Thomas, “Reach here with your finger, and see My hands; and put out your hand and place it in My side. Do not be unbelieving, but [stop doubting and] believe.”

without understanding, untrustworthy, unloving, unmerciful [without pity].

If we are faithless, He remains faithful [true to His word and His righteous character], for He cannot deny Himself.

But as for the cowards and unbelieving and abominable [who are devoid of character and personal integrity and practice or tolerate immorality], and murderers, and sorcerers [with intoxicating drugs], and idolaters and occultists [who practice and teach false religions], and all the liars [who knowingly deceive and twist truth], their part will be in the lake that blazes with fire and brimstone, which is the second death.”