Im at the the red eyed nightmare boss what lvl should I be? I'm playing on proud mode.

you should be lvl 40-50

i beat him at 35 on proud just have once more second chance and leaf bracer

that and alot of ballonras and dark firegas I beat the game with nothing in my deck was ballons and dark firagas

I was about lv 33 when I beat it. I found Dark Firaga and Icebreaker worked well., just keep an eye open for how it'll attack next.