How do i got this bastard item?

I kill at least 3 or 5 g3 chameleos but still not get it.WHY??

just take it as Elder Dragon heavenlies, even though it is much easier to get one (in my experience) since killing Chameleos is really easy and less annoying then gravios or tigrex for example. and rathalos even though easy, didn't give them often enough except in the DoTK quests, which is annoying

the fastest way in my experience is punishment blade with armor skills: S+1, SS and EAU.
drink Mega juice then dance in his right hind leg (your left). you will flinch it quite often. keep hitting it and sharpen when needed.
it basicly trading 3-4 mega juice + 10-20 wheatstone with a dead chameleos every 13-18 minutes
don't forget to try to cut the tail (when it flinch) when it almost die. it will give you extra chance to carve the BEDJ

1. Dual Dragon Ultimus+ can also do the job perfectly. you can also remove the horn with it as a bonus. sadly this one is also a hard one to make.

2. If you have beat Ukanlos, Gradios Ultimus G is a good alternative for Punishment Blades. it need no heavenly

3.. Descendants of the King quest usually give at least 1 ian/los heavenly. But, it is one of the hardest quest in the game IMO. if you can handle it, that will be your best way to get ian/los heavenlies

other than that, good luck on farming. everyone who play the game honestly also had a hard time farming the rare materials.