As you can see,it didnt evolve from Machamp directly,but it had to go through several more evolutions before reaching the "Legend stage" and reach perfection.
Thousands of years ago,a Machamp tried to climb the highest mountain in the world,in order to prove his love towards his couple.
He wanted to demonstrate,not only his strenght,but also his will to survive for her.
He never returned.
It is said that he couldnt get down due to a neverending snowstorm,and had to survive with the little food he could find around the mountain,and inside its caves.
He also had to fight against the terrible creatures that lived up there.
The Machamp refused to die.
As he promissed,he would survive,to show his bride how much he loved her,and to return to her once more.
The years passed,and the bride finally died of old age,but he never found out.
He believes their love for each other keeps them alive,so that,when the storm finally subsides,they will meet again.
Eventually,he found peace through meditation and training,and became the strongest creature.
But the memories of his true love could not be erased.
The locals say that on full moon nights,if you pay attention,a roar can be heard coming from the mountain.Its the Machamp,mourning for his beloved one.
Thousands of years have passed,but the Snowstorm never subsided.