@FormerCrimsonKing: He's supersonic. Sesshomaru is also at this speed. InuYasha is capable of reaching this speed as well.
Amaterasu may not work on him, as InuYasha is wearing the robe of the fire rat. It protects him from heat and flames.
Meidou zangetsuha,Wind Scar,Adamant Barrage could also end this in a sec.
A rather unique match. Itachi's greater speed and use of genjutsu would make it quite difficult for Inuyasha to land any attacks on him while Inuyasha's durability would pose problems for Itachi to take him out with regular tactics. For anyone who has forgotten, Inuyasha's fire rat kimono gives him high resistance to fire attacks and regular bladed weapons, which means shuriken and any fire jutsu (which includes Amaterasu) are gonna be ineffective against him. Not to mention that Inuyasha has done his fair share of tanking destructive attacks as he tanked having the Wind Scar reflected back at him from Kanna's mirror and Naraku's miasma attack melting down a whole forest. Itachi could still dispatch his foe with genjutsu or use of Susanoo's Totsuka Sword and Yasaka Magatama while Inuyasha has the stronger attacks of Tetsusaiga at his disposal to use on Itachi (Red Tetsusaiga and Kongousoha likely capable of going through Susanoo). This match could go to either character, but I'd give a slight advantage to Itachi here thanks to his greater speed and being a better battle tactician.