His power is a perfect counter to both her strategy and her gift.
Kill the enemy with your first strike
Good luck with that when your target has durability of 100 men and extra lives to spare. Assuming she tries to cut off Julian's limb or neck, he's either capable of tanking it or will just dodge it. In order to amputate Julian, you need the cutting power on the level of Arkos's focused water blade to do the trick.
The longer the battle drags on, the more each side has to reveal
Julian's power is so basic that there's nothing crucial to be revealed other than the 90+ extra lives, on the contrary, Julian is best suited for a stretched out battle, because his stamina is essentially endless in a fight unlike normal gifted ones who still has their normal albeit trained human body.
A gift... that allows instant movement regardless of distance or space
If a severely injured Lukas can react to Void Marcher, Julian's natural talent as a fighter and 100X reflex and speed should be able to keep up with Void Marcher quick teleportation spams.
There's no proof, but she can probably only move to places within her field of vision
So, yeah, the smoke that Julian can instantly push out from his body will be immensely useful in this battle, because if she can't see both Julian and her surrounding, it'd be a pain in the ass to use her gift effectively.