Forex trading has very high risks than bitcoin or altcoin trading. Forex trading also requires some huge amount to start trading. Unlike in bitcoin or altcoin trading which you can start for only 1$ or lower than that depending on what you can afford
In my opion, i don't think forex trading has the higher risky than Bitcoin or Altcoin trading at all.
The fluctuation of Bitcoin is really unstable and it could even reaches to 10-15% in once day and i don't think forex can reaches that much.