Getting beat down by demi-fiend

Im playing smt5v, first playthru, stopped at the emperean cuz i felt like I was approaching the end and i usually like to finish all the side missions before the main one but ooooooh boy has it been tough.

I cannot beat shiva nor demi fiend, theyre both so hard to kill. Shiva i feel like i have a good chance against and just need to respec towards that fight, while demi fiend is lowkey impossible.

For context im lvl 99 running phys crit murakamo build, ever since i got murakamo, i got complacent with my demon strategy so i have a lineup of random high lvl demons.

I guess for now i just want soft hints of what to do like if theres a subset of demons i should have, or what to look out for in general.