I'm not saying that he and the black widow will break up but if they did this girl would make a good girlfreind

i dont think so

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i dont think so

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how bout a townsfolk

Ms. Marvel would be better with Steve to be honest, they both have been through more together and have chemistry. But Bucky and Carol have nothing in common, sure they're soldiers, but that doesn't mean that makes them compatible to be in a relationship,  plus they barely even know one another, briefly working together on the New Avengers, the two haven't even said really even two words to one another, I don't even think it's fair to call them friends since they really don't even hang out or really interact with one another.
 
Black Widow has been set up to be Bucky's girl, they have been through much together, she understands what he's been through and knows the pain he has to deal with, and he knows her. They have that chemistry you need in a relationship, and honestly Natasha and Bucky are good together, they both complement one another both on the battlefield and as a simple couple. If you want examples, read the first story arc of the most recent Black Widow series, Liu really manages to capture what makes them both great together (even more than Brubaker), showing both the love and compassion they have one another, while also showing how they respect one another and who each other is....

I know it's wrong on oh so many levels, but it's be sooooo funny if Bucky & Rikki went out ;)

Silver Sable isn't dead. 
 
And he's fine with Black Widow.