Haven't played Dissidia, but I would argue Guy < Umaro! They have about as many lines, but one at least has the excuse of being a yeti and has some unique quirks like throwing Mog for one of his attacks. I can see arguing the other way, but at the very least they're close! So I think Guy's ranked in about the right place.
(minor Dissidia spoiler mentioned in passing)
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If it makes you feel any better, I personally think Umaro > Cosmos, since Umaro can at least throw sleeping/confused characters at enemies to wake them up; Cosmos is LITERALLY good for nothing other than sadfacing and suicide. Unfortunately I didn't get into this series until well after Umaro got ranked. Between the bottom 4, IMO, its
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(end Dissidia passing spoiler btw)
Guy > Umaro > LeBlanc > Cosmos.
And Guy > Umaro simply because being a berserker sucks for one's ranking.
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A staple formula for FF villains:
"They only do this, but lets kill them anyway!!!"