Link (Up B does not go as far in the air)
Samus (Up B, but only in the air, as doing it on the ground makes it gain the same distance as usual)
Luigi (down B when pressed repeatedly is nerfed, on both the ground and air)
Sonic (Up B, ground and air, as we all know)
Diddy (Up B distance is nerfed, ground and air)
Sheik (slightly, as the little bit of distance you gain when first performing her Up B is reduced)
Pit (his Up B is harder to control, and cannot go up as much)
Yoshi (slightly nerfs the distance gained from his Up B, but his double jump is unaffected)
Ice Climbers (both Side B and Up B are nerfed)
Dedede (Up B is nerfed on the ground and air)
Ness (his Up B is harder to aim because Ness falls faster, but double jump is unaffected)
Bowser (Up B gains less upward distance)
Toon Link (Same as Link, though obviously not to the same extent)
Lucas (harder to aim his Up B like Ness, but he stays floating a bit longer, so it's not as bad; double jump is also unaffected)