Which languages are the hardest to learn for English speakers?

One of my goals for 2015 is to learn more languages. I would like to become fluent in Spanish and then learn a little more Russian (I know very little).  I think Mandarin would be awesome. But, I’d be happy to be fluent in Spanish

You can see some of my memory training videos on languages at http://www.blackbeltlanguages.com/

Here is a great infographic on the hardest languages and easiest languages for English speakers to learn. Lucky for me Spanish seems to be EASY!