...I've had my solitaire take out a C'tan with nothing but a kiss. Pretty lucky, but not impossible.
You do realize that the kiss has the 6s specail rule too, don't you? Though it does allow saves, but that's irrelevant to C'tan, as their saves are invulnerable, aren't they?
Of course, as I remember it, C'tan have a rule which discounts that anyway, don't they? If not, my friend lied to me.