After knocking your opponent down, they will have a number of defensive options: Getup Attack, Roll Escape and Delayed Getup. There is way to cover more than one of these options. By simply walking back and staying out of the range of your opponent’s Getup Attack, you will avoid being hit and can whiff punish your opponent. Against some characters, you do not have to walk back as you can just block the Getup Attack and punish.
If your opponent does a Forward Roll Escape, you will also be able to punish the Roll Escape. If midscreen, this will not work against Backwards Roll Escapes. In the corner however it will work.
You will also be able to cover Long Delayed Getups. In order to do this, you must first wait for a Getup Attack or Roll Escape. If your opponent does not do a Getup Attack or Roll Escape and decides to do a Long Delayed Getup, you can react to the Delayed Getup and attack. This will cover all three options: Getup Attack, Roll Escape and Long Delayed Getup.
This will lose to Short Delayed Getup, or if your opponent decides to not delay their Getup. To counter these, you must time your attack so that it hits if your opponent gets up normally or does a Short Delayed Getup.