3 sentences

1. 她是这一切的罪魁祸首。

   tā shì zhè yī​qiè de zuì​kuí​huò​shǒu.

   She is to blame for all this.

   Source: OpenSubtitles

2. 她才是罪魁祸首。

   tā cái shì zuì​kuí​huò​shǒu.

   She is the one to blame.

   Source: OpenSubtitles

3. 专家指出，全球变暖是近年来极端天气的罪魁祸首。

   zhuān​jiā zhǐ​chū, quán​qiú biàn nuǎn shì jìn​nián lái jí​duān tiān​qì de zuì​kuí​huò​shǒu.

   Experts point out that global warming is the main culprit behind recent extreme weather.

   Source: Dong Chinese Dictionary