Ok. You're question is very stupid.
What you want to know is 'How come Haku's the only one who can preform single handed handseals?'.
On Naruto World we have several normal handseals that everyone learns (Boar, Tiger, Stuff). then, for special jutsus (Forbidden (Kage Bushin) and KG (Ice Release)), Ninja use other different handseals. Only a few of this handseals are single handed, since it's not common. Not many ninjas are able to preform this kind of jutsus. Many don't even have the chance to learn them.
So there's not much of a chance for a character to preform single handed handseals. If there would be one, it would be a KG possessor or a Forbidden user.
But one handed jutsus are very common with pure chakra manipulation. It has nothing to do with Haku, though.
