Luke's katana, embedded with tons of mana, froze the air around him and created something similar to an ice shield, and repelled some of the power behind the red giant's punches. Still, his speed decreased with each of the attacks. He also felt his bones cracking, but Luke didn't stop. He kept going because it was do or die now.
Eventually, Artheim healed enough to punch with both arms, so his attacks began to destroy the area with each one of those. His aura also grew more powerful to the point that even the wind and leaves that approached began to burn. His body also began to emit a lot of heat. Most likely, he never put himself under such strain, but he didn't stop. While feeling like his punches were ripping apart his own muscles, Artheim kept attacking.