I can't think of anything 'original' except for maybe one thing. I mean, everyone dislikes people who are not honest, not authentic, disrespectful, overly arrogant,...
But as a 'favorite' quality I often times see people mention loyalty. I suppose everyone likes someone who's loyal (makes sense) but I dislike loyalty that causes people to stop thinking for themselves. As in; I defend this person simply because they are my friend/partner, not because I agree with them. It's something I can't stand and I actually think it's manipulative (or it can easily become manipulative/toxic) to expect someone to always be 'loyal'. (I don't even deem not defending someone as being disloyal, but some people do) It's as if they are not even their own person anymore.
I appreciate my friends who speak up for their own opinion even when it differs from mine, who let me speak for myself (I can defend myself, I don't need anyone to do that for me). And I appreciate my friends even more when they accept the fact that I won't always stand by their side when they do or say something I don't approve of. We're still friends regardless- we don't always have to agree with each other, I want them to speak up and I hope they can appreciate my honesty too. Even if it means that they have to 'take down' my arguments in front of other people. I'd rather have that than having them 'agree' with me simply because they feel the need to defend me/not hurt my feelings (or for whatever reason someone would pretend to agree with someone).
It'd rather make me feel as if they can't be themselves around me, that would make me feel worse.
*To add: the loyalty I describe here specifically relates to behaviour in groups. It's different when you have a one-on-one argument of course. (If you can't even speak your own mind then your relationship is just extremely toxic. But the 'being loyal in a group to one another' is something I've heard about a few times. I think it's very odd.)
Edit: thinking about it. Not even only in groups. Even when someone talks about an argument/interaction they had with someone else and they expect me to 'take their side' simply because they are my friend/partner- you're at the wrong address. Some people do get butthurt over this. Luckily some people do appreciate to hear a different point of view from time to time. And I enjoy it too- when someone can look at a situation I talk about without having to feel the need to 'take my side', you don't even have to take a side at all. Just listen and say whatever you think.