Originally posted by Dreampanther
Based on the fact that a punch to the nuts nearly took him out of the fight it's clear he has some weaknesses - whether they are exactly the same as Cage's would be difficult to say. If his brain is not made of metal then I would say yes, it is possible for him to get knocked out and suffer from concussion, but how much force you would need to apply and where would only be speculation. The high impact close range shotgun blast upwards to Cage's brain was very deliberately aimed by Jessica to target his weakness, as was the punch to Colossus's groin.
Colossus was punched in the groin by someone with superstrength who was already capable of hurting him with regular hits. DP punched him in the nuts IIRC and DP just broke his hand.
So it's not like Colossus has a weakness there.