There's a long-standing saying that says that the smartest people have the least common sense. While it is true that most mad scientists are in fact dangerously maladjusted sociopaths, it must be remembered that “mad” can mean “eccentric and unorthodox” as well “batshit crazy.” Some may have benevolent or good spirited intentions, even if their actions are dangerous or questionable, which can make them accidental villains. While this kinder, gentler version of the mad scientist is not quite as common as his evil counterpart, he is a popular archetype in certain types of fiction.
http://www.ranker.com/list/the-greatest-fictional-mad-scientists/switchdoctor,
Dr. Julius No
Seth Brundle
Dr. Strangelove
Dr. Henry Jekyll
Dr. Emmett Brown
C. A. Rotwang
Dr. Victor Frankenstein
Dr. Moreau
Dr. Frank N. Furter
Dr. Frederick Frankenstein