"I need to stop this war."
No, you don't. You want to, but you don't need to. Clearly he has lost sight of their objective and what's at stake. Aside from Emily who has a friend here, they do not have stakes in this urban war. Sure, Zalord must die eventually, but Shion is obviously unprepared to fight him now and win, barring deus ex machina or some asspull at the end of this arc.
Haku is right, Shion's cornered; but only because he stubbornly clings to his hero complex that he is cornered. I wonder if this is the effect of "having let evil go" in his past that he seems to be overcompensating here. Maybe he's still haunted by the guilt of doing nothing to the chief's son and his thugs, and that children-killing noble that he thinks he can't stop now.
inb4 Ruin runs away again at the end of the battle.