AStoryForOne
On one hand I want him to balance break that MF right there, in the other hand it will make goetia know about MC power and can make countermeasures...
You completely forgot about the madness and insanity. Juggernaut Drive is often not a choice as it comes out on its own due to the user's troubled emotions and usually when using it, the user goes crazy. They cannot differ from ally and foe. Keep this in mind, Vali does not control the Juggernaut Drive, he enforces his will and even then, if he uses it for too long, it doesn't matter how much mana he has, he will still go berserk. In that case, we'll just have a Wilhelm living in Juggernaut Drive state with no sanity.
KissMyGloriousAxe:Juggernaut Drive is kinda overrated anyways... Though I'm not sure it would kill him. From what I'm aware Campione pretty much live forever; unless killed in battle. The authorities they get from gods; also come with infinite lifespan. Also I'm pretty sure he could use it in a similar manner to Vali; who uses his ridiculous mana reserves in place of lifespan. Not to mention the Kaleidoscope effectively grants him infinite mana; provided his body can handle what he pulls from other dimensions. Theoretically he could dump his entire mana pool into an attack; and regenerate it the next second- Though I'm not sure how his demonic energy plays into this; guess it depends on the author.