There's no visual difference in the question lists between those with upvoted answers and those with answers but not upvoted.
Currently, if a question has no answers at all, you see this:
If a question has one answer that has been upvoted at least once, you see this:
If a question has one answer that has never been upvoted, you see this:
In other words, you can't tell if a question has likely been answered well vs. answered poorly/unknown.
This means that questions that still need attention (because either the existing answer deserves an upvote or a better answer is needed) don't stand out at all from questions that have an answer with at least one upvote.
If a question has one answer that has never been upvoted, you should see (something like) this:
Note: I'm not saying this is the best possible graphic, I just threw this together to get the idea across.
This will give questions with no upvotes a little bit more visibility while adding very little complexity to the UI.