Actually without the fiery epithets and depiction as a villain, Duryodhana was just an ambitious Prince or ruler who did not want to part with what he got .. rightly or wrongly..
Even Shakespeare's Macbeth was like that.
And a normal human being of any age or epoch would have been just like him..
The world was, is and will be full of Duryodhanas..
Ultimately his ambition and reluctance to give up what he possessed was the cause of Bharatha war..
The description of evil deeds and the unsavoury portrayal was all just like adding sauce or ketchup to the dish..
If he were a nice persons and had the kingdom, still he would have tried to hold on to it..
But then in every story we read in life Duryodhanas will be there, showing up even without any conscious invitation..
It is just a reflection on a down to earth human mind.
And without the diplomatic and soldierly talents and the expertise of the Lord Krishna as a tactician, Mahabharata would not have been what it is..
I do not think Duryondhana would have given up the kingdom without fight even if he were a nice fellow..
But poetic fancy, once the characters were put in place, just gave different colours as to the personal preferences of the various stakeholders..
And Shakuni was just a sidekick.. a sort of villainous joker.. and nothing more.
Let us consider the core.. the root.. and the twists and turns in the epic Mahabharatham .. and the various climaxes..
We can see the presence of Krishna almost everywhere..