As for the question whether the Mendoza’s nature was violent, I think the answer is “no”.
At the beginning of the movie The Mission, the character Mendoza appeared in the image of a ruthless slaveholder. He trafficked in natives for interests. He showed no sympathy for these natives and regarded them as tools for making money rather than people. Actually, to some extent, I thought that he certainly deserved his woman’s affair with his brother. How can a woman be in love with a so ruthless man?
However, Mendoza suffered a lot from killing his brother. If Mendoza’s nature was violent, he would not feel so guilty. Because a violent man should be used to killing, besides, it seems that his brother was the wrong person for taking other’s woman. Mendoza could have defended himself, saying that he was fooled by anger.
On the contrary, he chose to climb the falls, tied to a large and ungainly bundle of weapons, for atonement. In the halfway, a companion cut off the rope because the bundle stopped Mendoza from advancing and dragged him back. Mendoza found the bundle and tied it up again. For him, it was a true atonement, rather than a form.
Afterwards, Mendoza made a cook but he put too much salt. He explained to the priests, saying that he was trained as a mercenary, not a cook; in view of this, so I think he was not born violently. Instead, Mendoza was trained to be violent due to the historical background. People who were violent could survive in times of disorder and use their skills to make fortune.
Nevertheless, in the late stage of the movie, Mendoza, who was quite unwilling to spear a pig after atonement, took weapons again for protecting natives. He realized that religion could not protect natives from profit-first Spanish and Portuguese settlers. He became a violent man again using violence.
I think the contrast in the movies is bitter satire. Mendoza, who used to be a ruthless slaveholder using violence against natives, had to fight against settlers for natives. Mendoza’s change is a tragedy.