A few of these can be DIed such as Down Air to Fair or Bair. In these situations you will want to use dash attack to follow their DI. Dairs hits do true combo together but the direction the opponent is launched at depends on SDI. You will also need to follow their DI to prevent them from falling out of this, if you miss the landing hitbox you will be stuck in landing lag and be unable to continue your combo.
Against some larger fastfallers you may opt to use Up Air at lower percents. This can lead into a surprise juggle and can rack up more damage but is a bit more risky. At higher percents only Fair and Uair will work reliably (if they are not in Up B Hammer range) Fair or Bair can also lead into a Wall of Pain at medium percents.
The Up B Hammer actually has a pretty wide range on most characters, but is somewhat DIable. You do have good control over your direction with Up B but depending on Rage and percentage it may not true combo or the opponent may end up outside of range. At higher percents or with high rage Kart Dash will true combo into Up Air for a KO. Kart Dash to Footstool is a True Combo, however the opponent has time to react before the falling Kart hits them.. This can still be used to catch opponents offguard but due to the high damage true combos off of down air it's usually best to go for that until around 20%.
Neutral Air is very reliable, but does low damage and doesn't lead into anything else.. pretty much all of your other options have potential followups and Wall of Pain potential.
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