"I am the punishment of God...If you had not committed great sins, God would not have sent a punishment like me upon you."
- Temujin the great chief
Someone like Temujin will appear till the end of times in our realm. Until people will learn to be kind to each other.
Since everything that has happened in the past is all 100% in accordance to God's plan. Then yes, perhaps Temujin is shaped to be such brutal character as a 'punishment' to other brutal characters.
Yet definitely Temujin is NOT the character who STOPPED the circle of brutality.
He was also a very spiritual person who prohibited lying, respected other faiths and made anything possible to make his people happy. He established such peace in his realm that a young virgin with a bag full of gold could walk without being molested. What "barbarians" they were... hm?
Just few example of what Temujin did during his life.
- Murdering his own brother while he was 14
- Sacrificing the life of his own followers to win a battle.
- Killing his own blood-brother turned rivals named Jamukha
- Torturing his rivals by boiling them to death.

- Mass murder of Chinese populace (approx. 1 million deaths)
- Massacre of Samarkand (approx. 10,000 deaths)
Not my favorite character, definitely...
But again you're correct if you're highlighting that no human is 100% evil, there are some good in Temujin. His love for his wife, his acceptance of Jochi as his own son (although Jochi was born from the seed of other man who kidnapped and raped Temujin's wife), his appraisal to talented people among his enemy (the chinese artisans and generals), his conception of meritocracy.
And you will also find some good aspect in Hitler, Stalin, Moshe Dayan, Ibn Saud.
Yet it's not an excuse for the brutality...