Go All Out.
Legion-1 reduced his speed from 736,000 to 536,000 by removing the enhancement of 100,000 from the domain of forge and shifting his divinity from speed to strength. This made him capable of an attack power of 410,000.
410,000 couldn't compare to the attack of 536,000 he had used earlier with divine strike, but it was still dangerous. With Smite's defense of 210,000, he would take on damage of 200,000. That should finish the job of killing him.
Most importantly, the attack was free. So Legion-1 could use it as much as he wanted without cost. When combined with his speed, the effect would become terrifying more than the previous attack. He would be able to take out both domain gods in a second.
Even Smite recognized the danger of his intentions as soon as he saw 9 Crowns shift his weapon into a bow. He knew he had to dodge, but he also knew he wasn't fast enough. So he used the one divine spell in his possession that will definitely hit 9 Crowns.