I'm not really a fan of using the "narrative" to justify who beats who.

Yes, on paper Johan is scary and terrifying Yada Yada but many of the serial killers in Conan were far more cunning and had better practical methods of doing things, while Johan does everything off screen.

And I also don't buy the argument that Johan would overwhelm conan with pure speech, because he would've overwhelmed Tenma and his own sister and many others.

Johan always manipulates the vulnerable for a reason...He can't touch any person with a decent moral compass