Most mtn lion attacks on humans aren't successful in terms of the intended outcome. So, on that front, you have an attack and you have a "successful" attack. Reportedly, cats don't like a fight so, if they don't land deliver a lethal attack on the first attempt and there is resistance, they tend to give up. So I've read, at least. I was using the term "successful" in relation to the outcome of actually being killed. Attacks are more common than "successful" attacks/kills. From what I'm reading, 15% of mtn lion attacks on humans are successful.