Actually, i don't believe that the menge sharingan would tickle Kyubi...

The mengekyou is an illuison attack that makes you see and feel the illusion, yet i doubt that Itachi could illusionize (create an illusion of) something which could hurt Kyubi...

what could he do? make Kyubi feel swords cutting his ultra though mountain crushing body? the fox is so big that it's hard to miss him with any weapon, so it's obvious that mortal weapons don't do shit to him...
next on line would be mental pain, which won't work cuz Itachi doesn't know anything about Kyubi and his mental weaknesses (and that's only if he has weaknesses, or mentality).

Kyubi was stopped with an etheral being (death) becuase it was the only way, if he was weak enough to be illuisioned out of existence, he wouldn't have lived long enough to become a legend...


that's what i think, at least...