Fallout 1 and 2 almost literally let you speech your way out of the end boss (though less so in Fallout 2), and that fact is part of what made those fallout games great (i.e. investing in Speech and Charisma instead of gun skills was not a dead-end for finishing the game). You could kind of do that in F:NV, too. So I'm perfectly fine with Obsidian giving players a non-violent option for Ukaizo... with the new DLC and megabosses it's not even the hardest fight in the game anymore. Still, I wish it was a bit more clear about how to avoid it and not, so it's less of a surprise when players don't get the fight.
yes, but that is not the same. You talk him out of it DURING the final confrontation ( of sort) . You see him, you talk to him, and yes, you can decide at that moment to avoid combat.
The whole encounter is not determined by something seamingly irrelevant you did hours of gameplay before