you can do the phase skip at phase 2 but the timing is pretty tight and there is some luck involved, Elizabeth will move to phase 2 when you get her HP down to 13k, but you ideally want to damage her for at least 8k moving in to phase 2, if you only damage Elizabeth 7k in phase1 then you just have to reset xD
as soon as elizabeth goes into phase 2, your mc has to have a charge already ready , ideally, a concentrate, and elizabeth with debuffs, and hit it with almighty, then switch up your persona to one with Strike Repel and Endure, ideally, you also want to buffs and debuffs active for this moment for a decent damage, i got Elizabeth down to 9,800 hp in this vid before using Armageddon
Enjoy!
also to note that you also need the Fortune Teller buff that accelerates your Theurgy faster
also this run has no Telos xD

MC Equips:
Lucifer's Blade
Armor of Light
Divine PIllar

Timestamps:
0:00 - Intro
1:10 - Phase 1
13:34 - Phase 2
16:22 - Persona Builds