In the course of your study, have you come across any historical record of monarchs or rulers expressing regret upon witnessing their regime collapse before their very eyes?

by Futarchy

Perhaps stating what should have been done better, or what mistakes were made.

sterboog

There's the famous story of Croesus (nearly) being burned on a pyre by Cyrus the Great.

There's a preamble to this story a bit early in Herodotus between Croesus and Solon which is referenced here. (tl:dr of the Solon story - Croesus shows Solon all his great wealth in his palace over the course of several days, before asking Solon who the happiest man was who he had met in all of his travels, Croesus thinking Solon would name himself. Solon replies several times with different, average, non-wealthy people who are all also dead. Croesus asks Solon if he despises him so much that he is not even in contention for being the happiest man compared to these dead men. Solon informs him that fates change, and while you may be happy now, it is no guarantee for the future, and as such no man can be counted truly happy until he is dead.)

This part of the story starts out after Lydia (of which Croesus is King), has lost a war to Persia led by Cyrus the Great. It is also the source of the story some may have heard where Croesus went to an oracle (actually several to test them first) before declaring war on Persia, and received in response that if he were to go to war, a great empire would be destroyed. Receiving such an oracle, he went to war in full confidence of his victory. Unknown to him at the time, the great empire that would be destroyed would be his own.

Herodotus, Book 1, chapter 85-88:

So the Persians took Sardis and made Croesus himself prisoner, he having reigned fourteen years and been besieged fourteen days, and, as the oracle foretold, brought his own great empire to an end. Having then taken him they led him to Cyrus. Cyrus had a great pyre built, on which he set Croesus, bound in chains, and twice seven Lydian boys beside him: either his intent was to sacrifice these firstfruits to some one of his gods, or he desired to fulfil a vow, or it may be that, learning that Croesus was a god‑fearing man, he set him for this cause on the pyre, because he would fain know if any deity would save him from being burnt alive. It is related then that he did this; but Croesus, as he stood on the pyre, remembered even in his evil plight how divinely inspired was that saying of Solon, that no living man was blest. When this came to his mind, having till now spoken no word, he sighed deeply and groaned, and thrice uttered the name of Solon. Cyrus heard it, and bade his interpreters ask Croesus who was this on whom he called; they came near and asked him; Croesus at first would say nothing in answer, but presently, being compelled, he said, "It is one with whom I would have given much wealth that all sovereigns should hold converse." This was a dark saying to them, and again they questioned him of the words which he spoke. As they were instant,º and troubled him, he told them then how Solon, an Athenian, had first come, and how he had seen all his royal state and made light of it (saying thus and thus), and how all had happened to Croesus as Solon said, though he spoke with less regard to Croesus than to mankind in general and chiefly those who deemed themselves blest. While Croesus thus told his story, the pyre had already been kindled and the outer parts of it were burning. Then Cyrus, when he heard from the interpreters what Croesus said, repented of his purpose. He bethought him that he, being also a man, was burning alive another man who had once been as fortunate as himself; moreover, he feared the retribution, and it came to his mind that there was no stability in human affairs; wherefore he gave command to quench the burning fire with all speed and bring Croesus and those with him down from the pyre. But his servants could not for all their endeavour now master the fire.

Then (so the Lydians relate), when Croesus was aware of Cyrus' repentance and saw all men striving to quench the fire but no longer able to check it, he cried aloud to Apollo, praying that if the god had ever been pleased with any gift of his offering he would now come to his aid and save him from present destruction. Thus with weeping he invoked the god: and suddenly in a clear and windless sky clouds gathered and a storm burst and there was a most violent rain, so that the pyre was quenched. Then indeed Cyrus perceived that Croesus was a good man and one beloved of the gods; and bringing him down from the pyre, he questioned him, saying, "What man persuaded you, Croesus, to attack my country with an army, and be my enemy instead of my friend?" "O King," said Croesus, "it was I who did it, and brought thereby good fortune to you and ill to myself: but the cause of all was the god of the Greeks, in that he encouraged me to send my army. No man is so foolish as to desire war more than peace: for in peace sons bury their fathers, but in war fathers bury their sons. But I must believe that heaven willed all this so to be."

So said Croesus. Then Cyrus loosed him and set him near to himself and took much thought for him, and both he and all that were with him were astonished when they looked upon Croesus. He for his part was silent, deep in thought. Presently he turned and said (for he saw the Persians sacking the city of the Lydians), "O King, am I to say to you now what is in my mind, or keep silence?" Cyrus bidding him to say boldly what he would, Croesus asked, "Yonder multitude, what is this whereon they are so busily engaged?" "They are plundering," said Cyrus, "your city and carrying off your possessions." "Nay, Croesus answered, "not my city, nor my possessions; for I have no longer any share of all this; it is your wealth that they are ravishing."