You need to catch it like 4 times, each in a different mode! You probably won't need help with the defence mode. With offence mode, you should use stuff that will make him stop for a while. For agility, use your plusle/minun. For normal, you need to be prepared for ANYTHING. It can change from normal, to agility, or to offence or defence. Normally that would not be a problam, but n this case, you have to capture it in normal to win. Only normal. If you capture in anything else, it will go to normal, then use a huge attack, then change a few moments later.