its not wrong, the translators made a (rather dumb ) mistake.

in katakana, shi could be meant as "si", if it were a foreign word...but if it were a japanese word, why change it? silly translators...

anyway, its a tie between the kadaj / cloud fight, and the sephiroth fight.

the kadaj one had the jenova music (really cool) and the sephy one had OWA, really really cool.