Either answer is a bad thing.
Metroid boss fights are never finished with a single sneak attack, she needs to have a couple of forms to scan.
Or, option 3: It's an entirely new power suit for Samus, and a new body for Duo. Neither of them are entirely familiar with it, and they probably haven't figured out its most powerful attacks yet. So they made a wild guess.
I agree with Squeejee on the Punctuation.
@Corey: Option 4: Samus is a Ranger, not a Rogue (although she does have a high escape artist check). She therefore does not get sneak attacks.
And apparently the Duo suit allows for minor forms of expressions. Neat!
Silly LavosQueen-X, this is a shadowclone/After-Image distraction...
how did lavos get all that info when samus didn't say a damn thing?
1st, Super-intelligent alien life-form.
2nd, Lavos recognized the Chozo technology as it had been on the planet for a while, and the "something more powerful" is deductive reasoning plus probably an innate ability to sense inner strength (which can apparently be fooled if Lavos isn't paying attention.)
Those are my best guesses.
In the last panel, the second sentence should begin with "Were" not "Where".
I'd say Samus is a warrior. She has Greater Cleave (I forgot what it's called, but the beam that goes through enemies), Power Attack (Charge Beam), a combination of Spring Attack and Whirlwind Attack (Screw Attack), and she's demonstrated close combat ability in addition to her ranged combat ability, while rangers specialize in one or the other.
She still gets the benefits of a surprise round no matter what class she is, though, so sneak attacks don't particularly matter in this case.
Even if Samus does get the surprise round, none of those feats apply to a grapple check. I think crushing your opponent in a giant glowing fist falls under grapple, even if it does look like one of Bigby's hands.
Anyway, they can't "kill" Lavos in the conventional sense. In order to "defeat" it, I'd say they have to overwhelm it with strength. So it doesn't help to use up any attacks when its not paying attention to how outclassed it is.