Lu Chenzhou did not choose to meet force with force.
In the vast world, all things are possible. Having Immortal Armor does not mean invincibility—there will always be someone who can counter you.
Before reaching the rank of Great Grandmaster, facing this Black Death Great Demon King was indeed troublesome for him; even evasion was difficult. But now, having mastered [Walking in the Darkness of the World], with a single thought, he could enter the Shadow Realm and avoid the sharp edge.
No matter how fierce the enemy's attack, he existed in a dimension parallel to the real world, untouchable.
Of course, Lu Chenzhou could also not act while in the Shadow Realm; to launch an attack, he would have to take the initiative to leave.
Therefore, this was not invincibility. The reason he was able to deal with the Shadow Kill Clan back then was because his crisis perception was exceptionally strong—able to sense their attacks in the instant they struck.
