You won't be able to create spritefonts for languages like Chinese, because they have tens of thousands characters. Japanese is possible, but only for the hiragana and katakana.
If you need a universal object that supports lots of languages including Chinese, you will have to use Text object.
I usually just google the alphabet for a particular language, copy/paste it into Word, use Find/Replace to remove all unnecessary characters like spaces. Shift+F3 to change case. And that's it.