That's just the thing now, given how he appears to nonchalantly go through thousands of years and comes back seemingly the same as ever... either he is actually acting in those scenes for some role-play reason, or losing does something to the mentality or brain of men that get beaten. I'm leaning towards the latter in this case, because Luka in Paradox has done a terrible job of acting with a base-line level of humanity that I'd come to expect from... well, humanity in general. This was the case especially when the time for the Great Decision came up and he just stood around debating between the two preposterously awful choices of which kind of slavery you must commit to in order to unlock the third option. You don't get the choice to look at Hell World and Angel World and go, 'No, fuck all of you, I'd rather everything dies right now and be reduced to formless primordial chaos than persist in that atrocity they call an existence for people.' Make it lead to an instant Game Over even, but just the presence of such a choice would at least show in some way that Luka considers the choices in front of him to be inhumane enough to warrant thinking about just not accepting them.
What it really comes down to that Luka is barely human, something that I've kind of always felt about him even in the OG MGQ, and the more I progressed through Paradox and getting the summary of how it ends slowly solidifies that stance. His mentality is far more in line with angels if anything, especially considering his perspective on the passage of time is similar to them with how easily he brushes off going through thousands of years without it having seemingly any effect on his personality whatsoever. I'm not saying this as a mark against the story's quality, but... I mean, it always comes back to the same thing for OG MGQ and all of Paradox for me:
I have a frustratingly large amount of questions and barely any answers to properly perceive what it even means to live in that world, whether it's as a human, monster, angel or a FUCKING UNDEAD (seriously, what the fuck is their undead existence like and why is there no consistency about them as entities, are they happy, tormented, suffering, blissfully ignorant?!). And I can't even begin to answer anything like that before the thought process runs into a contradiction or plot hole or parody element that intersects with the central story in such a way that it makes you wonder what is and isn't actually meant to be taken seriously anymore, because the parody or joke elements are sometimes actually intertwined with relevant parts of the plot without which the story couldn't progress.
... I really should stop here, I'm getting recursively more wound up over this than necessary over questions that will probably never be adequately answered, I just think that for what the story and world were, it feels like it had a chance to be so much more than what we were given.