I'd say do one of two things to make this level 1 balanced. Either
- Make it easier to cancel and give it a little more startup time (It would still be able to be activated while invisible)
This wouldn't cripple his level 1 too much as it would still have the advantages of being able to be used while invisible and it still has that insane hitbox.
- Make it so Sly can't use it while invisble (Current startup time and still hard to cancel)
This would make it still almost imposible to stop from happening and still quick, but the fact a Sly would have to go visible to activate it, makes it far more obvious when he is going to use it. This would also mean dodging it would be much easier.
If anything were to happen to his level 1 it should be one of those, not both. Got it, SB?
Sly can't dodge supers himself nor can he block any hit confirms into a super so allowing him an unstoppable level 1 is fair enough especially since it's awkward to combo into compared to most of the roster.