"Asterion and Niko" I feeling there isn't much animosity with them at all after their talk and duet unless Asterion still has some mixed feelings in the the previous argos has done to him and how Niko looks exactly like them, even if he hasn't done any harm to him (if the MC wasn't tricked at the start). I can imagine Asterion might struggle to separate Nikos' from the Argos role still
I agree, that's why I put animosity in quotations. You would expect there to be beef (heh) between Asterion and Nikos; especially if you didn't trick Argos twice. A combat competition is a good chance to subvert those types of expectations. There might be some but after their chat and if they carried on an online relationship, I could see Asterion being understanding of the situation (especially if Nikos tells him everything about the intent of the Argos role) and be forgiving. Though I could also imagine Asterion being playfully rough and intimidating with him, all in good fun.