My suggestions for this is...
If G-ranked, you will start in a random area, if ypur lucky straight in the nest with the rathian, kill that first if you didnt start in area 5(tips for killing)
Hammer(preferably onslaught hammer)
2. if hammer flash bomb and triple pound and keep doing until dead/when its gets into rage start to super pound it trying to still flash bomb it.
3.Then go for rathalos
Greatsword(preferably one with blue(at least green)sharpness and attack 800+))
2.if great sword flash bomb it, chop off its tail and keep hitting head (only in flash bomb)
3.then go for rathalos
Dual sword, dont use this...
lance(dragonrider spear if possible, one with 400+ attack and blue or green sharpness)
1. no need to flash bomb just headlock
2.its dead do same with rathalos but flashbomb.
And if it works congratulations!!! looks like christmas came early