I don't see anything wrong with your fanarts. The reasons might like what inspector and the otjers said, and another reason I want to add is maybe it was because they just don't like to have fanarts to be made out of their characters. And there's indeed some artist that didn't like that (don't wanna point fingers here, since it is one's preference).
Another thing, this is just my assumption and I'm taking a lot of salt there, so don't take this as offensive.
First of all, we don't know how the offensive fanarts and the replies of those thinking your arts is offensive to them, so we don't really know the bigger picture of who's really in the wrong here, so it might be best if you describe the arts and replies you've got from said artists here, if possible.
The thing is, and once again, this is just my assumption, the thought of you offending them might be because you're the one who thoughts that they think the fanarts you've made is insulting by reading their simple replies since you often thinking negatively.
You often think that everyone hates you, but the truth is it's not. They don't think you are a jerk, but you're the one thinking that you yourself is a jerk.
Maybe everything is just a simple misunderstanding, and you're just thinking too much. I don't know.
I don't particularly know you or know them, so I don't know what's what, so I'm sorry if this sounds as offensive to you.
Cheer up, mate. Don't dwells top much into this and you can try to make fanarts of some mainstream media, like, popular animes? They don't usually think too much about the fan arts made about their characters (probably...?).