General Dalton McGinnis is a former high-ranking officer of the United States Marine Corps.
He is first mentioned in Chapter 15. Claire Underwood hesitantly tells her aide in the same episode that she went to college with McGinnis. Frank is due to pin on his four star general rank and tells Claire - in a rage - he cannot go through with it because he knows of the incident in which she was raped by McGinnis. She convinces Frank otherwise, as she evidently has other plans in mind.
In Chapter 17, Claire reveals in her interview with CNN that it was McGinnis who sexually assaulted her. However, she embellishes the story after prodding by the interviewer whether or not she has ever been pregnant. Claire then admits, falsely, that it was McGinnis that got her with child while they were at Harvard together, although it is revealed that he did indeed sexually assault her and at least three other women during his service in the military.
In Chapter 25, it is revealed that McGinnis was court-martialed and found guilty of rape and other crimes. He received a dishonorable discharge from the military and was sentenced to 40 years of prison.