According to data reported by the famous anime called MyAnimeList , the first episode of Shingeki no Kyojin: The Final Season was the most watched premiere among the website's users. As of Monday, 144,668 users listed the anime as “watching” on their accounts, surpassing the third season of My Hero Academia , which had recorded a total of 107,042 viewers.
In response, MyAnimeList noted that spam accounts are being counted in the rankings, but still, Attack on Titan The Final Season is still the number one debut, even after discounting all users who listed the anime with a “1” or a “10” in the evaluation part.
The final season of Shingeki no Kyojin premiered on December 7th.
Source: ANN