The worst professor I have ever had not only in Columbia but also throughout my entire education history. His class is the total opposite of clear-explained, and he doesn't speak English. Most of the international students speak better English than he does. The most important, he is so indifferent and so cold. He truly doesn't care about his students; he ignored all of my emails, which I consider extremely rude. I had a really really important issue to negotiate with him, but he ignored all of my emails. I could say that he ruined my life for now. I don't know if things will work out a few years after, but it is impossible for me to say anything good now.