Unless the 2nd K gives an alternative meaning to the domain .. then you are essentially trying to sell them something they own the trademark rights on. So while it really depends on the specific domain (you will NEVER get accurate trademark advice from someone who doesn't know what the actual domain is), it could land you in trouble.
Obviously it all depends on the price as well .. if you offer it to them for $99, even if it is illegal .. they might just pay you anyways because it will be much cheaper than the alternative .. but they could theoretically sue you if they think it's worth it.
Again .. it depends entirely on the exact domain .. but sounds to me like you're infringing on their trademark and you might be better off simply deleting the domain. If I were you I'd get advice from someone or people you trust who actually know what the domain name is.
As a basic rule of thumb .. even if a domain or brand is not the exact same spelling .. it is still covered if it is similar. For example .. Coca-Cola would still hold trademark rights on Koca-Kola under all the TM catagories they operate under. Same thing for Cocca-Cola or CokeCola .. or anything that could be deceptively similar or confusing be a trademark/UDRP judge ...