Antares

Antares was the King of Dragons and the Monarch of Destruction. He was also the strongest Monarch and the final antagonist of Solo Leveling. Antares was a handsome middle-aged man with long red hair, a neatly trimmed beard, glowing red eyes, and a dark red tail. He also wore silver-red armor with a high collar and a reddish-brown tailcoat. He leads an army of dragons including Kamish who was considered as the worst calamity humanity ever faced. His abilities are for example his destructive dragon breath which could even eliminate Sung Jin-woo's immortal shadow soldiers. He thought against Jin-woo twice: in the first battle he completely overpowered Jin-woo, but was beaten by the rulers in the end. The second time they fought, was because Jin-woo asked the rulers to use the cup of reincarnation another time to fight Antares all by himself to reverse the losses that were made through Antares. In the end, Antares also lost that battle, but through the hand of Jin-woo.

(Source: Solo Leveling Wiki)