All quotes from the New International Version, ©2011:
Matthew 12:39
He answered, “A wicked and adulterous generation asks for a sign! But none will be given it except the sign of the prophet Jonah."
Matthew 12:41
The men of Nineveh will stand up at the judgment with this generation and condemn it; for they repented at the preaching of Jonah, and now something greater than Jonah is here.
Matthew 12:42
The Queen of the South will rise at the judgment with this generation and condemn it; for she came from the ends of the earth to listen to Solomon’s wisdom, and now something greater than Solomon is here.
Matthew 12:45
Then it goes and takes with it seven other spirits more wicked than itself, and they go in and live there. And the final condition of that person is worse than the first. That is how it will be with this wicked generation.
Matthew 16:4
"A wicked and adulterous generation looks for a sign, but none will be given it except the sign of Jonah.” Jesus then left them and went away.
Matthew 17:17
“You unbelieving and perverse generation,” Jesus replied, “how long shall I stay with you? How long shall I put up with you?”
Matthew 23:33-36
“You snakes! You brood of vipers! How will you escape being condemned to hell? Therefore I am sending you prophets and sages and teachers. Some of them you will kill and crucify; others you will flog in your synagogues and pursue from town to town. And so upon you will come all the righteous blood that has been shed on earth, from the blood of righteous Abel to the blood of Zechariah son of Berekiah, whom you murdered between the temple and the altar. Truly I tell you, all this will come on this generation.
Matthew 24:34
Truly I tell you, this generation will certainly not pass away until all these things have happened.
Similar sentiments about "this generation" in the other gospels. Later on...
Acts 2:40 — With many other words he warned them; and he [Peter] pleaded with them, “Save yourselves from this corrupt generation.”
Philippians 2:15 — “children of God without fault in a warped and crooked generation.” (Referencing disobedient Israelites in Deuteronomy 32:5, "They are corrupt and not his children…")
Hebrews 3:10 — That is why I was angry with that generation; I said, ‘Their hearts are always going astray, and they have not known my ways.’ (Paul was referencing Psalm 95:10. Again, disobedient Israelites.)
So, who was Jesus and his apostles speaking about? Was it his footstep Christian followers then, or now? Obviously not. These scriptures address and reference a corrupted Hebrew regime.
~Sue