Shiki vs. Shirou
"If powers are at max and we ignore the point of self-destruction caused from overflow
then Shiki will winn. No matter how much Shirou makes swords,
Shiki will keep "killing" them. It's a different story if it's possible to use
a "Mana Burst" like Excalibur."
1. Most probably referring to Archer-Arm Shirou but it could just as well be UBW Shirou. In either case if we ignore the fact that both of these people aren't going to have a future left after the fight, then Shiki wins. UBW Shirou is more of a gattling gun type anyway so that would be more appropriate for a killing one after the other.
2. Killing a Noble Phantasm, even a traced one, will cause problems apparently. "self-destruction due to overflow" in the case of Shiki could either mean the amount he has to deal with or the nature of Noble Phantasms (even traced) or a combination of both.
3. Interpretation of last line by some is that Shiki can't kill Excalibur. Interpretation by others is that Shiki can't do anything about an energy blast.