Translated Labs

You said:

I hate Zubat. They're so common, so hard to level up (until level 15), and so weak before then.

into Japanese

私はズバットが嫌いです。それらは非常に一般的で、レベルアップするのが非常に難しく(レベル15まで)、それ以前は非常に弱いです。

Back into English

I hate Zubat. They are very common, very difficult to level up (up to level 15), and very weak before that.