Equals?

"Kill Switch!" 

Two variants of the House of Shadows' attack collided. 

One was imbued with dark aura and the other with miasma. Their collision resulted in a mild explosion.

Keith grinned. "And here I am to think that losing your relic made you weaker." 

"If anything, I'm 10 times stronger than I was that day." Ace referred to the day their father took away the Heart of Malacoda from him. 

"That's too bad, I'm 100 times stronger, Kil Straight!" Keith used the attack Kira used earlier.

He became a blur to the eyes of normal spectators and moved faster than light. 

Clank! His dagger was blocked ny Ace's dagger. They both wore grins on their faces as they tried to exert power and force over the other. 

"I see we're using our entire arsenal, hehe." Said Ace. "In that case," He forced a break and jumped in the air. Tightening the grip of his dark aura blades he shouts, "Black X" sending the twin aura slash waves at Keith.