In a violent sense, the worst persecution of Christians is probably in some of the countries of the Middle East which have Islam as a majority religion. North Korea, with its state atheism, is another major region where Christians are violently persecuted. We should never use this as an excuse to hate Muslims, however, or to fear them. I say this because fear and misunderstanding related to Muslims does no good for the Christian faith.
I am not going to make the hackneyed and oft-repeated claim that Islam is a religion of peace (something which is, unfortunately, not always true, as you can obviously see watching the six o' clock news), but most Muslims are non-violent, and the more common varieties of the religion do not encourage or condone terrorism. Terrorism in the Middle East is often more political than religious, at least when directed toward outsiders, and receives religious support.
As far as non-violent persecution is concerned, it probably comes more often from secularism. It's more common in general, particularly in European nations.