I would agree and maybe replace aggressive with mean. As in no "mean snakes" as they have zero human emotions.
Aggressive could be used to describe a feeding response one snake's VS another's. For instance my boa has a far more aggressive feeding response than our Royal's. Or consider in general terms, that maybe a certain species IN GENERAL will be more apt to defend itself by striking.
For instance a Royal python's natural defense is to BALL up, other species have marked tails that resemble a head so potential predators don't attack their head, while others will strike.
I guess it all depends on how the word aggressive is used.
I tend to agree with mumps and don't think there is a such thing as a "mean" snake, and aggressive can be looked at differently depending what characteristic you are speaking of.
Mumps/Chris, you would be a good person to ask seeing as you've raised large snakes.
In general, what species has been the most difficult for you to deal with initially? What takes the longest to settle down? Some snakes are obviously better for beginners than others.