O Pārtha, that intelligence which wrongly understands the ‘right’ and the ‘wrong’, what is ‘to be done’ and what is ‘not to be done’, is rājasa.
It is not enough if the intelligence is sharp and perceptive. It should reason out matters properly. Rajo-guna distorts thinking leading to all kinds of violation. Duryodhana exemplifies this the most.
Totally intolerant of the prosperity and excellence Pandavas achieved in Indraprastha, Duryodhana invited Yudhishthira for a dice-play in Hastinapura. With the help of his uncle Shakuni, an expert in foul-play, he got Yudhishthira stake his kingdom, brothers, himself and their wife Draupadi, and lose them one after another. Then Duryodhana sent Pandavas with Draupadi on a 12-year forest exile followed by one year incognito life.
Completing it all, when Yudhishthira asked for the kingdom back, Duryodhana refused, stating they could fight and get it back. He violated all norms of ethics and propriety, rejecting the advice of Bheeshma, his own parents, and Vidura to mend his ways. The delusion and havoc rajo-guna causes are untold indeed!