I don't think Damian is the killer. There was a scene where he discovered a knife in the dining car of the train and showed it to Lily, and it has his fingerprints on it. That tells me he's not the killer.
But yeah Chance is obviously the victim.
And JG is doing "mistaken-identity-knifing" again, because JG repeats things.
I will try to recall this from memory. I might make a few errors but here is the gist:
Victoria and Amanda look nothing alike, but when Amanda was new in Genoa City, Amanda's ex Ripley was stalking her. There was a big gala or event at Newman Towers.
Victoria and Amanda were both wearing white gowns or pantsuits and their hair was about the same length.
In a less-than-bright hallway near the elevator, there was a slight resemblance from behind if you couldn't see skin color or determine exactly how dark their hair was.
Anyhow, Ripley was in a hurry, saw Victoria from behind, thought it was Amanda, and stabbed Victoria by mistake.
So yeah it's likely that JG will repeat the "hasty mistaken-identity stabbing in poor lighting" scenario again.
But I don't know who the killer will be.