Are there any "infamous" mathematicians who have discovered a famous or useful equation?

Answer 1

There have been plenty of mathematicians who have done so. Euler, Pythagoras, Euclid, Taylor, Newton, Cantor, Mandelbrot. But what do you mean by an "infamous" mathematician? Bad reputation?

Answer 2

One example I know is of Évariste Galois, a French Mathematician who is "infamous" because of his stupidity. He got himself killed when he was only 20 but the work that he did in those twenty years was pure genius. He solved some long-standing problems. Supposedly he died in a duel and his work was literally frantically written the night before he died because he knew he was going to die tomorrow.

Read about him here.
http://en.wikipedia.org/wiki/Galois

Answer 3

Umm... Einstein? Hawking?

Edit: Pythagoras (not proven, but credited)

Answer 4

Yes.