I really don't like Astarion at all. He gives me bad Twilight/True Blood vibes and I hate, what those and similar books/movies did to the vampire genre. Plus, he tries to kill me in the beginning and I really don't care about his 'tragic' backstory, when he himself is just a selfish and evil asshole.
So yeah, he is my least favorite character.
The feeling is usually mutual in my playthroughs, since I like to play good characters and he hates my guts. I did kill him, send him away and give him to the Gur in different playthroughs. It was very satisfying.

And yes, I tried his romance, it was awful, didn't like it.

"We are all stories in the end. Just make it a good one."

Doctor Who