Re:Zero kara Hajimeru Isekai Seikatsu 3rd Season Episode 12 Discussion

"If Regulus had the notion of doing so, he could have completely invalidated Reinhardt’s attacks with his [invincibility], and gone on to kill the somewhat troublesome Subaru and Emilia.

Despite this, he was deliberately eager to accept Reinhardt’s attacks directly, and thus was unable to put this acute plan into action.

Although, this was not to say that Regulus valued any high-handedness of spirit.

Rather, this decidedly further proved the nature that he’d supposedly cast aside.

—This man, Regulus, without using all his power to make everything succumb, could not stop.

Therefore, not crushing the meddlesome Reinhardt or just ignoring the provoking Subaru, were not decisions he could make in battle.

Assured by the premise that he could be neither injured or defeated, he needed to force his opponents to completely surrender, and leave their spirits defeated and broken— a man who knew only this way of battle.

...

Subaru slowly breathed deep, then slowly released the breath.

Then, glanced toward Regulus who watched them in silence. Regulus did not obstruct their conversation, just rested on his wrists as he waited leisurely.

Subaru: “Aren’t you a bit too relaxed?”

Regulus: “Aren’t I usually relaxed?”

Any trace of failure and the like, not even a speck remained.

Regulus had revealed all his preparations, and wanted to do away with Subaru. In truth, Regulus’s authority [Lion’s Heart] was perfect. After clarifying its key points, victory was still placed somewhere nigh unreachable.

However, precisely because he was convinced of his impending victory, would when confronted with Subaru’s struggles and efforts, watch from aside without intervention.

He had no idea what was happening. That point, was the same for Subaru himself."