Originally Posted by mustachepete
Quote
In his mind, if he showed any mercy or forgiveness to anyone who "injured " him--even his own brother-- (as he put it to Cardinal Lamberto in III), it would be viewed as a sign of "weakness" by enemies and friends alike--and would endanger his life. "


This all runs back into the earliest conception of the movies, and into the novel. Michael is a rationalist - the mathematics professor - and the inheritor of what Coppola called Vito's "intelligence, cunning and coldness." He just does calculations in his head, and dishes out what's deserved, no matter who's on the other end of it.

In the novel, Kay reflects that she loves that Michael is "always fair." Fairness can have a dark side - when crossed, a fair person can proceed completely without conscience in settling the score. That's Michael.

. I mean I definitely wouldn’t call Mike fair lol. Maybe in his own mind but he did also kill women too. Whether they were in the wrong place at the wrong time doesn’t matter. Tom bluntly asked him “Do you want to wipe everyone out”? Mike tried to rationalize it as it being his enemies but it’s obvious he had gone way too far and murder had become a first resort. But again what did Mike gain by killing Fredo at that point? Besides guilty that would haunt him the rest of his life.