I don't know if this has been brought up here, but I had a lot of trouble with that Aegon, but this Morning I decided to try to take him with my 4-Star Magik. I'm running MD, so after a 5-Hit Combo, and backing off until his Furies expired, and sometimes having to repeat once, I had 3-Bars of Power. I hit 5 more times to bring up more Furies, then launched that Sp3 to take big chunks of his Health down. Repeated a few times, and ended the fight with 99% health.