This is guaranteed on several characters, but most importantly, it works on Sheik. The only way to escape it is to DI down on the F-Throw and shield, but Kirby can change the combo in several ways to cover this. He can start the combo with N-Air/U-Air/D-Tilt > Grab, which makes it so the entire combo is guaranteed. If he starts it with N-Air or U-Air, he only needs one U-Tilt to footstool, and doesn't need any pummels. If he starts it with D-Tilt, he needs to pummel once before F-Throw, and then only needs one U-Tilt.Along with that, to get more damage, Kirby can reverse U-Tilt so it hits the 5% hitbox, then reverse it again for U-Tilt's Sourspot into Footstool. If he can condition the opponent properly to airdodge or try to attack him, he can D-Throw > D-Air after the F-Throw > U-Air and continue the combo using one U-Tilt, allowing him to do around 96% instead. If you get the U-Tilt > D-Air near a ledge, you can fast fall into a footstool to outright kill the opponent.This is guaranteed on King Dedede and Bowser, regardless of DI. F-Throw > Footstool > Grounding Stone works on both of them from 0% to 25% with proper DI, so Kirby can get a ton of damage this way. He can footstool DK after F-Throw, too, but can't confirm into Grounding Stone due to how high DK pops up, along with his incredibly high air speed.Unrelated to these combos, but @ RK Joker brought up a good point on the Kirby boards. If you DI away from F-Throw, Kirby's B-Throw has you DI in. This means that on characters B-Throw > B-Air works (around half the cast), Kirby can get the combo at higher percents against opponents who try to DI away from F-Throw (which is the best option against it).