Who was Shakuni? Why he played very dangerous role in Mahabharata?

According to Shakuni ,There is no point ,if you have an enemy ,you are pinch him ,you are biting him, spiting on him ,you are irritating him, you are abusing him , All these are ways of fools . Because if you are doing all these things to your enemy , your enemy go stronger and stronger ,and finally you will die ,not your enemy .So once you recognise your enemy just kill him.There is a story behind Shakuni .Shakuni was brother of Gandhari ,When Gandhari was married to Dhritarashtra ,and After marriage over ,They realise that Gandhari was technically a widow ,as She was married to a goat . Dhritarashtra got very angry .So he puts Gandhari Father and all his brothers in house imprisonment. And there was a law at that time to kill some one , reduce food amount day by day ,Slowly peoples will die .So same was happening with Shakuni and his Father and Brother . Slowly they where dying . But Shakuni Father and brothers planned , only one person will eat. and it was Shakuni . So at-least one person will be alive in the end .Slowly every one was dying.Shakuni Father forced Shakuni , to eat his brothers organs. Shakuni started eating his brothers organs .At the end when his father was dying , he said to Shakuni ,cut my Fingers and make dice out of it ,It will help you to win any game. Shakuni did same, he makes dice of his father fingers.This is one of reason why he always win  dice game .All these pains keep reminding him self of revenge ,He never forget .One day Dhritarashtra realise this one person is very brave ,he cal be free, and can be the part of our kingdom. Dhritarashtra did the same .Once he came out he made good friendship with Duryodhana .And Started filling all the evil things in Duryodhana mind .And We all know in end what happens in Mahabharata.Shakuni was limp ,there was also a small story  , When they were in house imprisonment ,at that time , Shakuni Father took his walking stick , and breaks Shakuni legs ,Shakuni screamed ,Shakuni asked why? His Father replied, it will reminding you these days which we are facing .In the end , Shakuni was successes what he wanted to do , he did every thing to make Duryodhana enemy of Pandavas . Duryodhana was so blind ,that he was not able to understand Krishna as most powerful .He created dice game .He cheated Pandavas and  made Pandavas Duryodhana Biggest enemy .The youngest of the Pandava brothers Sahadeva had taken an oath to revenge Draupadi's insult and sworn to kill Shakuni, the mastermind of the Mahabharata war. As sworn, Shakuni was killed by Sahadeva on the eighteenth day of the Kurukshetra war.Shakuni was already knows that , he will die , But he always remember his father words . He only aim was to destruction of whole kingdom , and he did it .