Eleanor Shellstrop believed that she was a bad person who accidentally ended up in the titular Good Place, but the very first episode dropped several hints that it was actually the Bad Place. This twist wouldn't come until the end of season 1 when Eleanor finally had her "holy forking shirtballs" moment. On her first day in Michael's fake Good Place, she had been too concerned about anyone finding out her secret to realize that even Chidi, Tahani, and Jianyu (Jason) didn't belong in the Good Place either. Still, she would have noticed the signs if she had been paying attention.
https://screenrant.com/good-place-episode-1-eleanor-bad-twist-clues/