Super-glue + plastic = garbage.
Sorry. I've been a Superglue devotee my entire hobby life and if there is one fact I've learned the hard way it is this one. I tend to not even let superglue near anything clear (or transparent) plastic anymore, because even if you don't get it on the main surface of what you are working on the chemical reaction of the cyanoacrylate can "fog" the edges of your piece.
You can try Super glue remover and it might clear it off some, but the base damage will always be there.
You may be able to salvage the visor to use as a pattern, though. I think I've read about some welding visors that members buy for their buckets. I haven't researched it too much because I'm not at the helmet stage yet.
