Real Bible Translation - Matthew 21:30

And he who has drawn near to the Second, said the same thing. And the one who has been separated said, 'I don't desire.' And finally, he who has regretted himself, went off.⁴⁰

Julia Smith Literal 1876 Translation:
And having come to the second, he said likewise. And he, having answered, said, I, Lord: and he departed not.

LITV Translation:
And coming to the second, he said the same. And answering, he said, I go , sir; but he did not leave.

ESV Translation:
And he went to the other son and said the same. And he answered, ‘I will, sir,’ but did not go.

Footnotes

This passage is translated from the earliest manuscripts. Later manuscripts made a real hack job of the passage.

The word used here is not "repentance":

"Rather “changed his mind,” felt regret but not repentance or Metanoia, a deeper and more lasting feeling: see ch. Matthew 3:2.

According to a well-supported reading the cases of the two sons are reversed. The first agrees but goes not, the second refuses but afterwards works in the vineyard. The variation is interesting, because it points to an interpretation by which the two sons represent Jew and Gentile"

(Cambridge Bible for Schools and Colleges)

Strongs #G3338, "μεταμέλομαι" (metamelomai) means "to change one's care or interest for another," implying a change of mind or repentance characterized by regret or sorrow. It denotes a reconsideration or remorseful reflection on past actions or decisions.