Warning: SPOILERS for Black Clover chapter 341
Lucius Zogratis might be Asta's ultimate big bad but the real foes who would have been perfect for Asta to fight to the death in Black Clover will never have to battle him in such a capacity.
This isn't to say that Lucius is not a formidable foe. He possesses soul manipulation magic, which has already turned Sister Lily into a Paladin in earlier chapters of Black Clover. Since he shares the same body with the ostensibly deceased Wizard King, he can also wield Julius' all-powerful time magic, which has proven to be quite helpful for Asta and the other Magic Knights of the Clover Kingdom. But as a weapon used against them? It will prove to be quite problematic. Moreover, Lucius has apparently killed and/or taken over the body of the most powerful wizard who justified Asta's existence as a formidable mage. Although Yami was the first to recognize Asta, nothing trumps recognition from the Wizard King, and Lucius took that man away from Asta.
But in recent chapters of Black Clover, Asta's training with Yami's sister Ichika and three of her comrades from Hino Country's ultra-powerful Ryuzen Seven prove that they would have been the perfect enemy for Asta to face. In chapter 341 of Black Clover by Yūki Tabata, Asta spars against Ryuzen Seven's Komari Imari, Daizae-mon O'oka and Jozo Hane-gatsuji. And although their ultimate move Zetten requires them to make their magic erupt all at once, Asta realizes that the actual eruption they create doesn't actually consist of magic.
Why Black Clover's Ryuzen Seven Are More Formidable than Lucius Zogratis
This puts Asta at a major disadvantage because his anti-magic actively seeks out and destroys any form of magic. This is what allowed Asta to be a formidable foe against powerful enemies and the ultimate ally for his fellow Magic Knights. Moreover, anti-magic gave him the means to become a Magic Knight and join the Black Bulls in the first place. The Ryuzen Seven would therefore be Asta's perfect and most dangerous enemy because he would no longer be able to use anti-magic, which is the true source of his power. Of course, thanks to the Ryuzen Seven, Asta is mastering Zetten himself, so he could still wield that attack against them. Their hypothetical battle would force everyone involved to rely on Zetten. Unfortunately, the Ryuzen Seven are much more proficient at using Zetten than Asta. By comparison, Asta can still wield his anti-magic against Lucius Zogratis to further protect himself from Lucius' soul manipulation and time magic (in addition to dodging) while attacking him with Zetten. Meanwhile, all Asta can do when fighting the Ryuzen Seven is dodge since his anti-magic can't destroy their Zetten.
If the Ryuzen Seven and all of Hino Country had been Asta's enemy from the start, then Asta would have been at any even worse disadvantage because they would have never taught him Zetten, rendering Asta completely useless against them. So although Lucius Zogratis is a perfect big bad because he's a more powerful version of Black Clover's Wizard King, Lucius's magic can't nullify Asta's anti-magic like the Ryuzen Seven's Zetten, the perfect counter to what justifies Asta's very existence as a mage in Black Clover.