I am playing through Genealogy of the Holy War for the first time (started going through the releases chronologically last year for the first time each, after only playing FEH in the past), and I read that Julius is kind of hard to kill in Chapter 10. I accidentally got too close, and he came out and attacked me, so I thought I'd give it a shot. I made a video recording since I was successful! I'm relatively new to this site, so hopefully it is ok to share stuff like this here. Enjoy!
I posted it on my FFXIV character Twitter (which I use in Japanese):