Michael Corleone is the last born son of Don Vito Corleone. Cold-blooded, ruthless, intelligent and smart, Michael has it all. He has got the same intelligence, cunning and strategic mind as of his father, but lacks the warmth that Vito has towards his family and friends. Initially, he does not want to get involved at all in the family business but fate has different plans for him. When his father is shot and is hospitalized and unable to get back to his work, Michael steps into his father's shoes. Unlike his father, Michael is not shown to be that much concerned with making friends how much he is with getting respect from his business partners. Although Michael succeeds even more than his father in making the business "legitimate", he ultimately proves to be a failure in his personal life where his father succeeded way more than him. This is evident from the fact where Michael on one hand starts losing his personal relationships one by one as he begins his life as Don Corleone.
One of the greatest tragedies that Michael faces in his life is the loss of his first wife Apollonia. It is after her death that Michael loses all of the emotions that he has. His eyes dead, debarred of all emotions, the new transformed Michael is only full of vengeance. Although Michael goes on to marry Kate, his utmost loss of the ability to love can be seen when he proposes to Kay. Devoid of all emotions, the proposal is coldly calculated to have family and kids who succeed Michael's business.
One of the tragic flaws that Michael shows throughout the trilogy is his inability to forgive. This leads him to alienate himself from everyone in his family and he in unable to make any friends. Not only does this tragic flaw of his personality lead to his alienation from his family and friends, it also leads him to do horrendous crimes like ordering killings of his own brother and brother in law.
Lastly, although Michael possesses the ability to think clearly under fire, it is his extreme logical and cold thinking that leads to his ultimate downfall which is most prominent when we see an emotionally bankrupt Michael holding his dead daughter in the third movie and dying alone in a big secluded house, in contrast to his father Vito, who died playing with his grandson in his tomato garden.