flub knee's "weak" hitstun combos into stuff in midair, like U-air, if you hit with the very end of it.
I don't think flub to sweetspot is a real combo, but more of a "DI" and movement limiter/trap, especially if the opponent doesn't have a double jump.
U-air only juggles if the opponent fails to trade hits/outprioritize or doesn't airdodge, but in my experience, it's usually airdodgeable. Of course, doing airdodge isn't always the best choice, especially if he hasn't started his attack yet (because U-air > opponent airdodge > sweetspot KoJ is win), but it pressures the opponent to react earlier due to its vertical reach in comparison to his normal jump animation, similar to how you can do that horizontally with Sonic's speed.
I don't think flub to sweetspot is a real combo, but more of a "DI" and movement limiter/trap, especially if the opponent doesn't have a double jump.
U-air only juggles if the opponent fails to trade hits/outprioritize or doesn't airdodge, but in my experience, it's usually airdodgeable. Of course, doing airdodge isn't always the best choice, especially if he hasn't started his attack yet (because U-air > opponent airdodge > sweetspot KoJ is win), but it pressures the opponent to react earlier due to its vertical reach in comparison to his normal jump animation, similar to how you can do that horizontally with Sonic's speed.