To be fair, Matt never "ruined" any of the women he's dated. As Elektra herself pointed out, a person can only take responsibility for the deaths they cause with their own hand. Karen's fall into pornography and drugs happened well after her break-up with Matt, and had nothing to do with him (the last time he'd seen her, on an adventure with Ghost Rider, she'd been a successful actress). Black Widow, Elektra and Echo all maintain friendly relations with him. Heather Glenn (the woman who wanted to be a CEO) was a victim of bad writing and worse characterization. Milla Donovan is perhaps the one who comes closest, but even she chose to pursue him, break-up with him, and then return to him. She wasn't without agency. That's not to say Matt Murdock doesn't have issues with women, but that the issues he has are a lot more complicated than is generally shown in superhero comics.

I'm not sure why writers chose Daredevil to be the hero with the worst love-life. Honestly, I find it a bit strange. Maybe it is partly because of the abandonment issues he has with his mother. Maybe it's also to be Marvel's counter-point to DC's Batman. It's kind of sad because he's a hero that could be super-inspiring for kids if his comics weren't so hell-bent on being dark and edgy.

Sorry, I've gone on for far too long...