Verlux v Crim:

TLDR: Naruto has good enough offense to harm Tian, but not good enough defensive measures to keep going

1. Due to starting in So6P mode, the speed equalization acts on So6P mode, not on Naruto's base. As a result, Monochrome would in fact halve his speed.

2. Naruto's organs are weak and while his argumentation that force would impact his organs is valid, fiction doesn't actually give a shit and there's an explicit scan saying they're weak so

3. Tian is very capable of hitting Naruto with the spear & the shockwaves, both of which are capable of killing him.

4. Monochrome probably wouldn't outright shut down his powers, but I'm pretty sure it could severely injure or kill him solely by pressure.

Unfortunately Naruto just doesn't have the defensive measures to keep going for this, so he gets tagged once and dies. While Naruto can harm Tian, I don't think he's nearly as capable of oneshotting.

Verlux wins.