Duryodhana is said to have been the villain of Mahabharat but is there any good in him? What are the good qualities of Duryodhana?
Duryodana was a good ruler and have always looked after his subjects. Only wrong in him was that he was against Pandavas and greed for their wealth. His character was praised by Bhishma, Drona, Vidura and others many times as well. And, he was a great warrior too.
His good behaviour is quoted in Asramavasika Parva by people of Hastinapura when Dhritarastra informs then about his decision to go to forest.
Verily, in this race of kings, there never wag a king who coming to rule his subjects became unpopular with them. Ye have ruled us like fathers or brothers. King Duryodhana never did us any wrong. Do that, O king, which that righteous-souled ascetic, the son of Satyavati, has said. He is, verily, our foremost of instructors. Left by thee, O monarch, we shall have to pass our days in grief and sorrow, filled with remembrance of thy hundreds of virtues. We were well protected and ruled by king Duryodhana even as we had been ruled by king Santanu, or by Chitrangada, or by thy father, O monarch, who was protected by the prowess of Bhishma, or by Pandu, that ruler of Earth, who was overlooked by thee in all his acts. Thy son, O monarch, never did us the slightest wrong. We lived, relying on that king as trustfully as on our own father. It is known to thee how we lived (under that ruler).
Well, one good trait is that Duryodhana seems to know he is Kali. While the Mahabharata does not state it, I am pretty certain Duryodhana is aware he is Kali and sabotaging himself on purpose. He quite clearly does not know the full plan which means there is someone bigger controlling him.
There are a lot of little things that give this away like Duryodhana being the real protagonist of the story (most of the major events are caused by his actions), him knowing things about the other races that appears nowhere in scripture other than him saying it, and his complaints mirroring those non-humans would have about humans. One big reason though is one of the few times the Mahabharata directly tells us what Duryodhana is doing, not through Sanjaya and not while he is speaking to the "good guys." While Duryodhana initially thinks of the experience as a dream, he remembers it later and makes decisions based on it showing he knows it to be true.
The most important detail is a comment that he does not tell people about the specific supernatural phenomena occuring. This makes no sense to say unless Duryodhana knows what is happening, unlike everyone else.
And Suyodhana thought that Karna and the Samsaptaka army were both able (to destroy) and intent upon destroying that slayer of foes, Partha. Thus, O bull of the Bharata race, the hope was strengthened of the wicked minded son of Dhritarashtra, of conquering the Pandavas. And Karna also, his soul and faculties possessed by the inmost soul of Naraka, had at that time cruelly determined to slay Arjuna. And those heroes—the Samsaptakas also—having their sense possessed by the Rakshasas, and influenced by the qualities of emotion and darkness, were desirous of slaying Phalguna. And, O king, others with Bhishma, Drona, and Kripa at their head, having their faculties influenced by the Danavas, were not so affectionate towards the sons of Pandu as they had been. But king Suyodhana did not tell any one of this.
"When the night passed away, Karna, that offspring of the Sun, with joined hands, smilingly addressed these wise words to king Duryodhana,
'No dead man conquers his foes: it is when he is alive that he can see his good. Where is the good of the dead person; and, O Kauraveya, where is his victory? Therefore, this is no time for grief, or fear or death.'
And having, with his arms embraced that mighty-armed one, he further said,
'Rise up, O king! Why dost you lie down? Why dost you grieve, O slayer of foes? Having afflicted your enemies by your prowess, why dost you wish for death? Or (perhaps) fear has possessed you at the sight of Arjuna’s prowess. I truly promise unto you that I will slay Arjuna in battle. O lord of men, I swear by my weapon that when the three and ten years shall have passed away, I will bring the sons of Pritha under your subjection.'
Thus addressed by Karna, and remembering the words of the Daityas and supplications made by them (his brothers), Suyodhana rose up. And having heard those words of the Daityas that tiger among men, with a firm resolve in his heart arrayed his army, abounding in horses and elephants and cars and infantry.
So powers of perception is a good quality and some of his apparent bad qualities are really intentional. Some of them are not though as he is described as wicked/vain.