I'd say Tyrande, Sylvanas and Nathanos have definitely made it harder for me to like any of them. I much prefer Shandris and Lilian compared to them.
I'm in the same boat that Sylvanas' fans basically make it near-impossible for me to like her character. But what drove things home for Sylvanas and Tyrande is how their characters interact with characters I actually like. Both act like villains and only one of them is that.