Princess / Swordsman spike

The Princess/Swordsman spike is a Peach, Roy, and Marth specific tech. It is done by using a counter to setup an invisible ceiling glitch, causing your next attack to knock your opponent at a different trajectory than usual. Specifically, if on stage it will send them straight slightly away and then straight down. If your attack knocks the opponent off-stage it will remove all vertical velocity of the knockback, but retain their horizontal knockback and hitstun. This turns strong attacks that have upwards knockback, into powerful spikes. Here is how to set it up:

How to perform

To setup the ceiling glitch, you need to press L or R to shield (for the best effect your shield should be decently small), release shield by letting go of trigger or using jump, roll, or grab and counter a grounded attack. Then you should hit your opponent while they are airborne.