You really need to tell us the context to get a good answer like jilar has explained.
"Stop, dammit!" sounds like something out of a Sherlock Holmes novel.
Changing the word order is what I was going to suggest, too. For some reason, it sounds more natural that way in English, even though I guess the Spanish order is more logical, since the important information is conveyed first.Shit! Stop! - more accurate although the word order is changed.
I think "coño" is used mainly as an exclamation of frustration, exasperation or (mild) irritation - at least in the Canary Islands. "Stop, dammit" sounds correct in this context as does "Stop! Fucking hell..." but I've never taken "fucking Hell" as very aggressive or profane. A possibility could also be "just stop!" or, if one is seriously annoyed, "Just fucking stop!"
I find that this "coño" or "joder" that comes at the end of an exclamation is quite hard to translate into English. As you said, "Stop, dammit!", although correct I guess, sounds strange. The most accurate translation I can think of is "Stop! Fucking hell..." but I don't think that "coño" or "joder" are as strong as that.
I think it's important to avoid personal insult, although I agree that it is natural in that situation in US English. But it is absent from the original and significantly changes the tone.Or to preserve the word order:-
Stop you bastard!
I'd love to know the context though.
tanto me imagino que diga coño como joder. No cambia nada en el sentido final aunque sean dos palabras diferentes.