Whenever you want to express something like "you did it again!" in Chinese, you generally want to use 又 (yòu).
Normally, 又 is used to express an action that has already happened again for (at least) the second time. It doesn't have to be in quick succession; it happened before, and now it's happened again.
又 + Verb + 了
"又来了" fits the above pattern, but is also a little tricky because it expresses something that is still ongoing, and has already started as the speaker is speaking. Literally it's say, "here it comes again," but it's more accurate to translate it as "there it is again," or "there [he] goes again." It indicates that the speaker is a bit annoyed that it happened again.
When it becomes clear that something is about to happen again, you can also use 又. It's almost as if it has already happened in your mind. In these cases, it's quite common for 又 to be immediately followed by 是 (shì), 要 (yào), 可以 (kěyǐ), 能 (néng), and you'll notice that there's often a 了, indicating that something is about to happen.
又 + 要 / 想 / 可以 / 能 + Verb Phrase (+ 了)