I believed his greatest strength as an Auror would be exactly what I saw in him in the first place -- the ability to think a few steps ahead of everyone around him. I thought his greatest weakness would be impulsivity, his willingness to leap out into the void without think through those steps -- again, a Gryffindor trait, and certainly one I saw in Ron, although sometimes that's its own sort of strength.

Of course, his greatest weakness, in the end, was the hidden loyalties I never saw -- the disease at the root of the plant, and his willingness to turn on Our Lord and bring about his doom.