Crossed Beak / Scissor Beak, can be severe, but many times, this beak malformation is not hazardous to your chicken's health. This condition can afflict any breed, but seems to be more prevalent in Easter Eggers or Ameraucanas.
My only experience with cross beak / scissor beak occurred with one of my Blue Wheaten Ameraucana pullets that I had so proudly hatched in a homemade incubator. Thankfully, her crossed beak wasn't severe and the problem didn't show up until she was several weeks of age.
I do remember being quite concerned that the poor baby would not be able to get enough to eat or have trouble free-ranging, but I needn't have worried. This sweet gal can keep up with the best. She eats as much as her sisters and is a nice plump size. My pretty Ameraucana loves to free-range with her buddies and has even tried her hand at being broody.
I trim her beak every 2-3 months with clippers, since the tips are not able to be filed down naturally, but other than that, she receives no special care and is now just over 2 years old. My Pet Chicken has some helpful information on Crossed Beak / Scissor Beak here.