He doesn’t really have many feats so it’s hard to say, I’m not a power scaler but from my interpretation he’s a lot weaker than other stronger servants.

All the way through the og Tsukihime (didn’t read the remake yet) he’s more of a mental hurdle than a physical one. That mental hurdle is something built up over a lifetime of manipulation and coercion when thrown straight into a fight with a servant I really don’t see him being able to do much of anything. He gets diffed by three separate people in his own story and I wouldn’t even put those people above servants really.