My advice from practicing with a rather good Arakune
-The majority of this battle is airborne. 2C is your best friend. If you see Arakune coming down for his 2A,B,C, use 2C. Worst case scenario, you both take damage. That still rids you of curse, and rids Arakune of his advantage if he has it.
-Air Dashing in this battle is a terrible idea. More often than not, you'll eat a cloud on approach. Follow the Nu-13 strategy and hop over, or better yet, wait for Arakune to come to you.
-2B and JB are good tools for this match-up. 2B is quick counter for his land-shark attack and keeps him within range for more dangerous combos. JB is quite often unexpected in the air, especially if you've been using JC constantly.
-If you block an air combo, Grab. You'll either air grab, or normal grab as soon as you hit the ground. While the air is more satisfying, its the not the best to combo into. You get the normal grab, you can combo into at least 3k.
-For meter use, all air specials (Hotaru, Tsubaki), are extremly effective. Hotaru can knock off Arakune in any air combos he might be in, and Tsubaki (which I've dubbed Fly-Swatter), knocks him out of the teleport 2 out of 3 tries.
-On the ground, not many specials make a difference until you can get in range of the Arakune. Renka is useful due to its speed, safety, and low hit. Enma is useful in certain situations, but you can go without it. The same goes for Gurren.
-Ground combat-wise,The two most likely techniques will be his 6C or Land-shark. Block the first hit of 6C and counter the following hit with 5D for a free combo. Land-shark is simple. Block low and punish.
-If you're gonna cut clouds, do it in the air, using JC or J2C. On the ground, you're suspectible to being hit by his JD bugs.
-6C is a dangerous attack to use, but if you land it and follow it with Shippu, you're guaranteed a very good lead. Arakune's health isn't as bad as Ragna's or Nu's but its pretty damn close. Landing a successful Shippu can really earn a good lead.
-His laser distortion (the one where he turns into spider and fires a beam into the air) is asking for trouble FOR ARAKUNE. Assuming its not part of a combo, jumping into it is not always a bad idea. If you're quick, and slash into the beam, that's a lot of meter gain on the auto-guard. If you're VERY good at it, try timing your JD while jumping into his distortion. At a decent height its a lot of meter gain if you keep JDing. If you're low enough, you can pull him right out of the distortion for a very nasty surprise.