King K. Rool (SSBU)/Up smash
A rising headbutt, followed by K. Rool falling on his belly. Up smash is incredibly strong knockback-wise while being reasonably well-protected, with intangibility and Belly Super Armor backing it up. Being frame 6, it can be used as a rather decent out of shield option to deny aerials on shield. It is also an amazing tool for ending stocks from mashing punishes out of down throw, hitting opponents during the 12 frames of popout lag through its impressive active frames. As a result, the move has a solid place in King K. Rool's kit.
However, the move has many issues. For starters, while the armor is useful, the move's damage can be used against it through counters. Vision with Buster, Tetrakarn and Gut Check can instantly break the armor should they counter the initial hit, and others will severely damage it while tending to avoid the rest of the hits. The move is also monumentally slow afterwards, with a FAF of 72. The hits after the first hit are generally quite useless outside of shield poking, with the 2nd hit's mid hit having the weakest meteor smash in the game and the 3rd hit never landing KOs. While it is effective for shield poking, there isn't much reward after either. As an out of shield option, up smash also tends to become more niche when players realize that the first hit - the one they're after - only really works on aerial opponents due to the jostling mechanics. Overall, if not used for mash punishes out of down throw, up smash tends to falter.