Patronizing and wholesome is the worst type of onee san. The appeal of the older sister is of a woman slightly more mature, but still in the same age range- old enough to know more about the world, but young enough to still fit in with you.
I would go as far to say that the appeal of an older sister can be found in any woman that is a single measure above your equal, be it in style, maturity, grace, kindness, or any quality we find to be most wonderful in people.
And attempting murder is peak sibling behavior.