Once you beat the game, a secret boss is available in traverse town. Go to the fountain area and from the manhole comes Julius. He is one tough boss, his attacks are fast, vicious and crazy powerful. An easy way to defeat him, however, is to stack ur command deck full of the balloon command and 2 curagas. Spam your balloons and try to goad Julius into running into them. Keep your distance, spam balloon, and use your curagas and you will do just fine

What level do you have to be for this to work?

Why not use Balloonga? It is much easier and safer to use.

Preferably maxed out(which I currently am not), but a decent level should work, 50+ should be good just have dream eaters that greatly boost your magic and defense.

 

True it is, I used regular balloon though. Although balloon would be better because the balloons are stationary and u can use them as traps, try to get him to run into them since he is relentless and constantly pursuing you.

Julius is pretty easy if you'r lvl 40+ and you got Second Chance+Once More, i k0ed him at Proud Mode lvl 41 (Sora) and lvl 39 with Riku.

 

A good command deck would be:

 

Sora:

 

2 Curaga's

Balloonga/Balloonra

Firaga burst

Ars Arcanum

Icebreaker

 

Riku:

 

Dark Aura

Curaga (2)

Icebreaker

Firaga Burst

Balloonga/Balloonra

 

Also, if you got Dark Roll with Riku you'r making the fight even more easier because you can dodge attacks at a very high speed rate.