Nope.

Oh! Of course, Tryndamere is the only male. >.>
On a more serious note: Vi is the only one with a cone shaped ability?
If that's not it, then is it lore-based? Appearance-based?

It's regarding abilities/mechanics.

Sivir is the only one who can't reduce any of her cooldowns without CDR.

I totally did not notice that. I guess you mean including Caitlyn's ult being interrupted (target dies before firing) and Vi's Vault Breaker not released?

Well, that's not what I was looking for. Nice answer though.

Akali is the only one with a stealth.
Sivir is the only one with a returning skillshot.
Ezreal is the only one with a global range ult.
Vi is the only one with a passive basic ability(not the innate, but denting blows).

It's one of those ones where the odd one is '______ is the only one withOUT a ________.'

Sivir is the only one without a dash.

NightmareLullaby already guessed that. It's true, but not what I wanted.

Kat because she has no steroids?