A yellow smiley isn't an attack, for one...nor does he require his Green Lantern ring to surf the net (though I guess he could create a computer facsimile and then everything would have a green tint)...and like I said, it was a flaw of the old GL rings. Now the only weakness lies within the willpower of the user, I'm pretty sure...I was never a big fan of any GL, really...
I think what we should focus on is the fact that we're being asked who'd be a "worthy match" for Crono...I don't think Q snapping his fingers would be much of a match at all, really...So maybe those kinds of instant death people don't count? Bye bye, Potter, no Avada Kedavra 4 j00!