Exactly. Let's also not forget the magical energy generated from hundreds of human sacrifices in a very specific place (a major confluence of Ley lines). The blood-line curse was dark, dark black magic. It was so bad, Odin showed real anger mentioning it and decided to get involved himself.
I also think it's a bit unfair to say one wizard killed the RC. Harry was not alone. He was the one who cut Susan's throat in the end. But he never planned the whole thing and he certainly couldn't have been there without the help of a lot of other people. Among them a god, a major league Winter Sidhe, all three Swords of the Cross, Bob, 11 powerful wizards, the Kenku, a Foo dog, a White Court vamp, Susan herself, Martin ... and last but not least internal division in the Red Court.
If any one person could be credited with pulling it off, it would be Martin. He might have been the one who planned it. At least the possibility of it happening. But I doubt he could have been sure it would happen exactly that way. That would be beyond stupid, because so much could have gone wrong.
Also he couldn't have done it, if the Red King hadn't decided to take revenge on
hisfamily by way of a generational family curse. There are many other ways to take out Eb and family, but the Red King chose
that way. Then everything had to be aligned exactly right to pull it off, remember it was some fast desperate thinking at the end for Harry to win, he was losing and little Maggie was about to get her throat cut.. It was the realization that Martin was a double agent, and the fact that he could message Susan quickly enough that it was him behind her daughter being in danger that pissed her off enough to lose control and kill him, then and only then could he stop it and indeed by doing it took out the whole Court.
Mira,
I totally agree that circumstances were special and need to be taken into account. However, my point is that just because there aren't all that many Wizards, as compared to the general population, as we've seen, numbers aren't everything. For all we know, the same curse MIGHT be able to be used against the outsiders. They might all be related. We really don't know.
All that being said, Harry can shape and change reality itself, with the proper preparation and motivation. That's whats so cool about being a wizard.
See above, Harry was motivated to stop his child and by extension himself being murdered, true, but he wasn't prepared or had a plan on how to stop it.. He didn't plan with with Susan before hand that he'd get her pissed off enough at Martin that she'd turn and rip his throat out and then allow him to cut her throat, setting off a chain reaction. While yeah, any wizard could have pulled it off, but in order to pull it off, all the ducks had to be exactly in a row... For the Reds it was the perfect storm of the Red King's own making..
So while yeah, it is an example of one wizard stopping a whole clan/tribe/group, it doesn't follow that it could be used against the Outsiders.. For starters we don't even know if they are related by blood as the Reds were. Then how do Outsiders reproduce? Then how do you find the youngest to sacrifice in order to set off the chain reaction? So while they are both fruit it becomes an apples to oranges example of what one wizard could do.