Surely a B.O.W.'s effectiveness was to be judged by not only the carnage it directly caused, but also that which it indirectly caused?
Surely a scientist was at least indirectly responsible for the devastation caused by his or her creations?
Surely everyone (except for Dr. Marcus's apprentice, whatever-his-name-was – Gherkin?) agreed that Alexia's talent for B.O.W. research and development was unsurpassed?
Therefore, he, Alexander Ashford, was the greatest B.O.W. designer in all of Umbrella, for he had created Alexia.
Just because a being wasn't sloughing off necrotic flesh or wriggling with inexplicable tentacles didn't mean it wasn't a weapon, after all.