Fury and Hunbaba were so easy at 60(Vaan=60, others=50-55) that I jumped into Chaos expecting to find maybe a slightly more difficult version of the two, but got smacked in the face. I didn't even have full health because I had just fought Deathscythe and I think got smacked by a trap too, so I was pretty weak. The difficult part was taking out the elementals before they swarm, which can be messy for the unprepared. But even with weak MP and low HP I took them out before they could get to me. Afterwards, just have to watch out for whirlwind which can one-shot someone, and Aeroja which can take out everyone if you're unprepared for it. I think, with a well thought battle plan, you could take Chaos late 40's early 50's. Maybe even earlier, especially with good equips and spells.