Krishna is good.
In Shalya Parva,Yudhisthira was in grief as to how he will behold the wives of Kauravas.
https://www.sacred-texts.com/hin/m09/m09059.htm
"It is we that deserve to be pitied in every respect, O Kaurava! We shall have to drag on a miserable existence, bereft of all our dear friends and kinsmen. Alas, how shall I behold the widows, overwhelmed with grief and deprived of their senses by sorrow, of my brothers and sons and grandsons! ..... We, on the other hand, shall be reckoned as creatures of hell, and shall continue to suffer the most poignant grief! The grief-afflicted wives of Dhritarashtra's sons and grandsons, those widows crushed with sorrow, will without doubt, curse us all!"
Duryodhana also abused Krishna about his actions during Mahabharat.
Sitting on his haunches and supporting himself on his two arms, he contracted his eyebrows and cast angry glances at Vasudeva. The form then of Duryodhana whose body was half raised looked like that of a poisonous snake, O Bharata, shorn of its tail. Disregarding his poignant and unbearable pains, Duryodhana began to afflict Vasudeva with keen and bitter words, "O son of Kansa's slave, thou hast, it seems, no shame, for hast thou forgotten that I have been struck down most unfairly, judged by the rules that prevail in encounters with the mace? It was thou who unfairly caused this act by reminding Bhima with a hint about the breaking of my thighs! Dost thou think I did not mark it when Arjuna (acting under thy advice) hinted it to Bhima? Having caused thousands of kings, who always fought fairly, to be slain through diverse kinds of unfair means, feelest thou no shame or no abhorrence for those acts? Day after day having caused a great carnage of heroic warriors, thou causedst the grandsire to be slain by placing Shikhandi to the fore! Having again caused an elephant of the name of Ashvatthama to be slain, O thou of wicked understanding, thou causedst the preceptor to lay aside his weapons. Thinkest thou that this is not known to me! While again that valiant hero was about to be slain this cruel Dhrishtadyumna, thou didst not dissuade the latter! The dart that had been begged (of Shakra as a boon) by Karna for the slaughter of Arjuna was baffled by thee through Ghatotkacha! Who is there that is more sinful than thou? Similarly, the mighty Bhurishrava, with one of his arms lopped off and while observant of the Praya vow, was caused to be slain by thee through the agency of the high-souled Satyaki. Karna had done a great feat for vanquishing Partha. Thou, however, causedst Aswasena, the son of that prince of snakes (Takshaka), to be baffled in achieving his purpose! When again the wheel of Karna's car sank in mire and Karna was afflicted with calamity and almost vanquished on that account, when, indeed, that foremost of men became anxious to liberate his wheel, thou causedst that Karna to be then slain!
Duryodhana said that if his opponents fought himself, Karna, Bhishma, and Drona, victor would never have been his.
If ye had fought me and Karna and Bhishma and Drona by fair means, victory then, without doubt, would never have been yours. By adopting the most crooked and unrighteous of means thou hast caused many kings observant of the duties of their order and ourselves also to be slain!'
Krishna then told Duryodhana who is actually responsible so he defended himself.
"'Vasudeva said, "Thou, O son of Gandhari, hast been slain with thy brothers, sons, kinsmen, friends, and followers, only in consequence of the sinful path in which thou hast trod! Through thy evil acts those two heroes, Bhishma and Drona, have been slain! Karna too hath been slain for having imitated thy behaviour! Solicited by me, O fool, thou didst not, from avarice, give the Pandavas their paternal share, acting according to the counsels of Shakuni! Thou gavest poison to Bhimasena! Thou hadst, also, O thou of wicked understanding, endeavoured to burn all the Pandavas with their mother at the palace of lac! On the occasion also of the gambling, thou hadst persecuted the daughter of Yajnasena, while in her season, in the midst of the assembly! Shameless as thou art, even then thou becamest worthy of being slain! Thou hadst, through Subala's son well-versed in dice, unfairly vanquished the virtuous Yudhishthira who was unskilled in gambling! For that art thou slain! Through the sinful Jayadratha again, Krishna was on another occasion persecuted when the Pandavas, her lords, had gone out hunting towards the hermitage of Trinavindu! Causing Abhimanyu, who was a child and alone, to be surrounded by many, thou didst slay that hero. It is in consequence of that fault, O sinful wretch, that thou art slain! All those unrighteous acts that thou sayest have been perpetrated by us, have in reality been perpetrated by thee in consequence of thy sinful nature! Thou didst never listen to the counsels of Brihaspati and Usanas! Thou didst never wait upon the old! Thou didst never hear beneficial words! Enslaved by ungovernable covetousness and thirst of gain, thou didst perpetrate many unrighteous acts! Bear now the consequences of those acts of thine!"
Duryodhana later boasts himself and how he enjoyed earth.
"Duryodhana said, "I have studied, made presents according to the ordinance, governed the wide Earth with her seas, and stood over the heads of my foes! Who is there so fortunate as myself! That end again which is courted by Kshatriyas observant of the duties of their own order, death in battle, hath become mine. Who, therefore, is so fortunate as myself? Human enjoyments such as were worthy of the very gods and such as could with difficulty be obtained by other kings, had been mine. Prosperity of the very highest kind had been attained by me! Who then is so fortunate as myself? With all my well-wishers, and my younger brothers, I am going to heaven, O thou of unfading glory! As regards yourselves, with your purposes unachieved and torn by grief, live ye in this unhappy world!"'
A shower of flowers fell on Duryodhana which made Pandavas become sad.
Sanjaya continued, 'Upon the conclusion of these words of the intelligent king of the Kurus, a thick shower of fragrant flowers fell from the sky. The Gandharvas played upon many charming musical instruments. The Apsaras in a chorus sang the glory of king Duryodhana. The Siddhas uttered loud sound to the effect, "Praise be to king Duryodhana!" Fragrant and delicious breezes mildly blew on every side. All the quarters became clear and the firmament looked blue as the lapis lazuli. Beholding these exceedingly wonderful things and this worship offered to Duryodhana, the Pandavas headed by Vasudeva became ashamed. Hearing (invisible beings cry out) that Bhishma and Drona and Karna and Bhurishrava were slain unrighteously, they became afflicted with grief and wept in sorrow.
This is where Krishna, in a deep voice defends himself.
Beholding the Pandavas filled with anxiety and grief, Krishna addressed them in a voice deep as that of the clouds or the drum, saying, "All of them were great car-warriors and exceedingly quick in the use of weapons! If ye had put forth all your prowess, even then ye could never have slain them in battle by fighting fairly! King Duryodhana also could never be slain in a fair encounter! The same is the case with all those mighty car-warriors headed by Bhishma! From desire of doing good to you, I repeatedly applied my powers of illusion and caused them to be slain by diverse means in battle. If I had not adopted such deceitful ways in battle, victory would never have been yours, nor kingdom, nor wealth! Those four were very high-souled warriors and regarded as Atirathas in the world. The very Regents of the Earth could not slay them in fair fight! Similarly, the son of Dhritarashtra, though fatigued when armed with the mace, could not be slain in fair fight by Yama himself armed with his bludgeon!
He later consoles them and told how even the gods trod in the same way.
You should not take it to heart that this foe of yours hath been slain deceitfully. When the number of one's foes becomes great, then destruction should be effected by contrivances and means. The gods themselves, in slaying the Asuras, have trod the same way. That way, therefore, that hath been trod by the gods, may be trod by all. We have been crowned with success.
Krishna also, adviced Duryodhana for peace.
https://www.sacred-texts.com/hin/m05/m05128.htm
Having, like a heartless fellow, done innumerable wrongs to the Pandavas and behaved so deceitfully towards them, thou seekest now to appear in a different garb. Though repeatedly solicited by thy parents, by Bhishma, Drona, and Vidura, to make peace, thou dost not yet, O king, make peace. Great is the advantage in peace, O king, both to thyself and Yudhishthira. Peace, however, does not recommend itself to thee. To what else can it be due, but to thy loss of understanding? Transgressing the words of thy friends, thou canst never attain to what is for thy benefit. Sinful and disreputable is that act, which thou, O king, art about to do.'
Krishna blamed the elders of Kurus for not binding Duryodhana which is true.
Hearing these words of Bhishma, the lotus-eyed hero of Dasarha's race, possessed of great powers, addressing all those (that were still there) headed by Bhishma and Drona, said, 'Even this is great transgression, of which all the elders of the Kuru race are becoming guilty, for they do not forcibly seize and bind this wicked king in the enjoyment of sovereignty. Ye chastiser of foes, I think the time hath come for doing this. If this is done, it may still be productive of good. Listen to me, ye sinless ones. The words I will speak will soon lead to beneficial results, if, indeed, ye Bharatas, ye accept what I say in consequence of its recommending itself to you. The wicked son, of ill-regulated soul, of the old Bhoja king, having usurped his father's sovereignty during the latter's life-time, subjected himself to death. Indeed, Kansa, the son of Ugrasena, abandoned by his relatives, was slain by me in a great encounter, from desire of benefiting my kinsmen. Ourselves with our kinsmen then, having paid due honours to Ugrasena, the son of Ahuka, installed that extender of Bhoja's kingdom on the throne. And all the Yadavas and Andhakas and the Vrishnis, abandoning a single person, viz., Kansa for the sake of their whole race, have prospered and obtained happiness.
Gandhari also thought that it was Krishna"s fault and cursed him.
https://www.sacred-texts.com/hin/m11/m11024.htm
"Gandhari said ... Since deliberately, O slayer of Madhu, thou wert
indifferent to this universal carnage, therefore, O mighty-armed one,
thou shouldst reap the fruit of this act. By the little merit I have
acquired through waiting dutifully on my husband, by that merit so
difficult to attain, I shall curse thee, O wielder of the discus and
the mace! Since thou wert indifferent to the Kurus and the Pandavas
whilst they slew each other, therefore, O Govinda, thou shalt be the
slayer of thy own kinsmen! In the thirty-sixth year from this, O
slayer of Madhu, thou shalt, after causing the slaughter of thy
kinsmen and friends and sons, perish by disgusting means in the
wilderness. The ladies of thy race, deprived of sons, kinsmen, and
friends, shall weep and cry even as these ladies of the Bharata
race!’"
Krishna said that it was Gandhari"s fault, not his fault.
"The holy one said, ‘Arise, arise, O Gandhari, do not set thy
heart on grief! Through thy fault, this vast carnage has taken
place! Thy son Duryodhana was wicked-souled, envious, and
exceedingly arrogant. Applauding his wicked acts, thou regardest
them to be good. Exceedingly cruel, he was the embodiment of hostilities, and disobedient to the injunctions of the old.
Why dost thou wish to ascribe thy own faults to me? Dead or lost,
the person that grieves for what has already occurred,
obtaineth more grief. By indulging in grief, one increases
it two-fold.
