What if THE ROARING KNIGHT were in rivals.
Jab: the knight will point forward, and a purple ray will emerge. It'll shoot out of it a bunch of small stars. They deal small damage, but if they leave the ray and stay out for too long, they'll explode and reveal small arrows. The arrows then chase foes.
The ray can be held.
Dash: the knight use the same animation he do before his "hall of swords" attack for smooth visual dash attack.
Side tilt: the knight will shoot forward a black blob that does a great knockback to anyone it hits.
Up tilt: the knight will spawn many small black blobs to move slowly upward, it'll be an improved version of the side tilt.
Down tilt: the knight will put his sword downward, in the same manner he did to kris after he "defeated" him. The sword will be quick.

Forward strong: the knight will slash the opponent infront of him, BUT ALSO will grow a small red line a few meters away. The line itself can also deal damage, not related to the sword strike. When a foe is hurted by the line, an additional line will be added for the next hit, up to total of 8 lines.
Up strong: the knight will be summoning a sword above himself. The longer you charge, the more swords appear (5 max). By releasing the strong, they will strike the ground underneath the knight. if all 5 swords appear, a titan will emerge from behind the knight to deal quick and powerful blow.
Down strong: the knight will spawn 4 swords on both sides (2 each) that move further from the knight. Then they aim to the opponent they hitted. If no one is hitted, they aim sideways.

Neutral air: the knight will surround himself with his swords in a circle.
For all the air inputs: the knight will leave a sword turned to the input direction. The sword stays for a few seconds and then dash forward that direction.
It can also be aimed diagnolly.

Neutral special: will take time to charge, but will unleash fast and strong sword slashes that launch foes on the final hit.
Side special: he will morph into the same sprite he did when he kidnapped undyne. This will be a bit slow but he will move to a great distance, carrying with him anyone he is hitting. Foes taken by him cannot move until the move end.
Up special: turning into a black ball and then can be moved to any direction input. Enter free fall afterward.
Down special: HOLDBREATH. the knight will turn faster for the next 20 seconds. After it end, there is a cooldown of 15 seconds.

Final smash: the roaring knight final attack.
Parrying: the animation he did as he blocked susie.
Dodging: turning into the same ball.