It would, but if you've already resolved an attack with the Slash Dragon in order to get it equipped with something, they're unlikely to have multiple threatening backrow. You'd be better off using something like Nobleman of Extermination at that point.
Well, it say "Target 1 face-up Equip <<Spell>> Card you control". Maybe thats why it cant be used on monster that equipped to Reli.
curious
ok so I've tried using it on a number of different equip spells, in several occasions, but I can NEVER activate it, only set. What the heck?
I know it was working before on black pendant, but can't even activate it now even if I do control the dark pendant and opponent has some set s/t in s/t zone...