Tomz

Best answer as chosen by Asker / Ratings
Wiseman is right about both, although Rathalos is very easy to take down with any G sword as long as you can predict his attacks (which is very easy). I did it with Great Serpentblade first time, use flash bombs to get some easy hits and after about 10 seconds lay the pitfall trap under his feat and wait for him to fall into it, then go for the face. This should weaken him severely, repeat with flash bombs but just hit until he snaps back out of it as it provides Rathalos with hardly any attack opportunities. If you don't have any flash bombs left then wait until he scratches the ground with his feat and go for the head, the time it takes for him to roar will give you enough time for a solid hit (or 3) to his head hopefully breaking off his crown. If he turn around fast then he's most likely going to charge, if he turns around slower then usually a fireball attack so get around him and attack the side of his head after he fires.