Now I don't know if there had been a discussion about it before, so if there is, please give the link.Â
In ATLA, Roku said that if the Avatar is killed in the Avatar State, the cycle will be over, i.e. Raava would be killed since the Avatar exists because of her. But in TLoK Book 2, it was revealed that Raava can't be destroyed permenantly, as she would reborn within Vaatu (Dark & Light can't exist without one another), which means that the Avatar can't be destroyed permenantly, as Raava could fuse with another human to make Avatar once again when she's reborn. But it contradicts Roku's saying to some extent (he said that the cycle would be over, and it will be, though temporarily if Raava is killed but he also said that the Avatar will cease to exist, which wouldn't happen). But the question is why Zaheer tried to end the Avatar and bring chaos by killing Korra in the Avatar state. It wouldn't end the Avatar for good due to the reasons mentioned above. What do you guys think about it?
I personally believe that since Zaheer was an anarchist, he wanted chaos, and for that he wanted to end the Avatar since it was the highest Authority. Killing Korra in Avatar State would end the cycle and though Raava would reborn till next Harmonic Convergence, it would take a lot of time, almost 10,000 years, and therefore there would be no Avatar during this period and the world would be plunged in chaos i.e Zaheer's goal would be achieved. Even if the Avatar is reborn after such a long time, it would not be easy for him/her to end the chaos present for thousands of years. (Also formation of Avatar requires a lot of spiritual energy, which could only be obtained from a Spirit Portal during HC as seen in Book 2)