He uses this in the mini avatar fights its a pain because once you get hit you can't run away to resummon carby. So maybe just summon carby once and let him die before the first Searing Light so carby takes the weight instead of you.
The description should be more along the lines of: This is Leviathan's Blood Pact ability "Tail Whip" which inflicts melee damage against the target, with the added effect of Gravity.
You can make a skill chain with Tail Whip. It falls into the category of the following Weapon Skills: Backhand Blow Gust Slash Cyclone Dancing Edge Red Lotus Blade Freeze Bite Raging Axe Gale Axe True Strike Earth Crusher Shell Crusher Sidewinder Tachi: Jinpu Tachi: Yukikaze Blade: To Blade: Jin Slug Shot Steel Cyclone
Just substitute Tail Whip for one of these Weapon Skills (i.e. Tail Whip > One-Inch Punch = Gravitation) Enjoy :)