Honestly, Character? Dialog? Plot? Setting? Bad Words? have all done it at one time or another. OK, maybe not bad words very often. On stage sex almost never. (I confess to a fault as a reader. I tend to page past such scenes.)
It is very difficult to enjoy a story if the character is not believable.
In truth I think being believable covers all the bases here.
A writers failure in any one of those categories is likely to kick a reader out of a story.
A really good writer can grab and keep a reader with any of them.
The bad news is that not all readers are going to be believers.