This is actually one of my favorite mangas. I am ambivalent about getting any pitchfork yet. Yeah the story is fucked up with that girl killing kids to target tools of the cult. They even announced in their dialogue "this is making us sound like the bad guys". And being so consumed with revenge against a 'world ending' cult, for a single person's sake, that you not only are willing to silence fatally the kids, but then immediately drop your mission and let them escape when it is that single person you're avenging. Completely fucked up and confused. And definitely surprising she drops the topic so fast that the guy knew where Orn was and immediately does some mission. You'd think she'd try to convince Orn to join her.
And yes, I don't like the introduction of hidden talents/powers for the sake of scaling. Let the MC take the L and work hard to get better. It seems unnecessary except as an insurance policy for plot armor, and to convince the reader that Orn could have won.
Now claiming that Orn is a tool of the cult, while Orn was kicked out of the party and Oliver was explicitly recruited to the cult: the only development on this that's memorable is the lady in the hero party acting sus. Then the nobles all act like Orn didn't mean shit. Are they going to reveal later Orn was recruited, had powers sealed, and afflicted with a mind control spell that he will later fight against? This cult has evaded so much exposition to the reader, the impression is it is supposed to be scary; but the manga has Orn say he can easily beat Oliver, and Oliver is somehow a key to their plan - enough to force a showmatch.
The author has handled redemptions well, as evidenced by the emotionally believable actions before this shit show; so it is possible the story ends up making sense.