Don't trade when he is active, if whoever it is trades say 10% of bund volume that leaves about 900,000 contracts a day trading that he isn't part of. Learn to identify these spots where the guy is active and just sit on your hands. Sometimes the best trade is to not trade. Have learned this sitting in the 10yr where flipping can turn into someone getting smoked on a 7000 lot. Nothing the guy does is illegal, it is just someone taking out small locals that lean on price levels when there is no real paper in the market. Yes there are risks if he has the book stacked and gets run over, but that comes with the territory.