To add to this. Make sure to make the correct choices in the fight. From what I saw here after completing the chapter (I only come here after I complete the chapter to avoid spoilers). Most people are losing the fight because they're making the wrong choices, not because their power levels are low. The choices are, stay back at glowing sword. Go all in. Do not evolve.
If this doesn't work then yeah it might be a power issue. I did it first try luckily and I only had 67 Power and 21 skill. Chose the eye, can't wait to see what it does.