Is Trump so much worse than the other Republican candidates? No, not really. On some issues, he's actually better, while on others he's just as bad as the rest of them, while possessing the virtue of being upfront and honest about exactly what terrible things he has planned.
Can he beat Hillary? Probably. This is the year of authenticity, and while Hillary is far and away the most experienced and capable candidate in the field, she's also the least authentic. Nothing about her seems real, and even after all these years you're not quite sure what he position is on anything other than a smattering of core concerns. If this was 1820, and Hillary was, you know, a guy, she'd be the hands down winner. But in 2016 the electorate seems to want an outsider, which means Hillary is toast.
Hillary's one advantage over Bernie in a race with Trump, is that the insult king would not be able to be as viscous with her. Call a woman something nasty, and you're a monster, but say the same thing to a guy and its just trash talk. Also, Bernie, I believe, can give as good as he gets. Would be interesting to see a gloves-off, all New York race between a Seinfeld Jewish guy from Brooklyn and an Archie Bunker German-Scottish guy from Queens? Maybe.