I think it's a combination of Angel basically dismissing Tess after he finds out her past, running off like a huge prat, and then--when he gets back--doing absolutely nothing. What is the use of repenting if you never do anything?! "Let her wake naturally"--oh thank you so very much, Angel Clare, that's all you can do? That's all you do in the whole thing! Oh my god, why are you such a horrible person? Maybe this comes of being weaned on stories where it's normal for the protagonist(s) will do something (anything) to help each other. I'm not asking him to whip out a weapon and fight through all the men surrounding them. But he literally leaves her to be killed.
Also, he never gets his comeuppance. At least the husband in the Mayor of Casterbridge does. No, he just goes off with Lizzy-Lou and presumably marries her in a bit. It reminds me of the closing stanza of "Clementine."
I really have to get around to reading Jude the Obscure. I don't like Hardy's poetry (I can't get over his Titanic poem. It was an abomination) but I love his novels, and that's the last of the big ones I haven't read.