There may be lot of cases like money laundering, terrorist funding by using the crypto coins. But still we can't blame crypto coins for all these. These kinds of activity was still there when there was no cryptocurrency. And even for today, I don't think that crypto is the main medium of payment for the terrorist group. the terrorist group used to active mostly in the remote parts of the planet and internet connection is a big issue there. Another thing is that the value of the crypto coins are so much volatile that terrorist groups do not take such a market risk.