Every clan have some sort of special ability , so im not sure what you mean by this post.
Not every clan however, has a gene based ability that you get because of emotions (not training). Most clans don't have a genetic ability that allows you to oneshot the likes of perfect jinchuuriki, kages and other powerful opponents with the literal bat of an eye (sometimes without even knowing that you have that power).
When was the last time you saw a Nara or an Akimichi oneshot a perfect jinchuuriki or kage using a power that they had never even used before or didn't even know they had (and with the bat of an eye)?
I can think of a couple of times that this has happened with a certain clan *wink wink*.
When did you last see a Sarutobi or a Hyuuga solo all 9 bijuus within seconds and reduce them to pets with not much more than a glance? I'll wait.
Also, every other clan only gets one weak ability. Sure they can train and come up with variations of said one weak ability (ie. mind body transfer vs mind body destruction, or shadow possession jutsu vs shadow strangling jutsu). In the end though, it is still just one ability (and usually a very limited and not very strong one). Kishi didn't even allow these people to branch out and learn non-clan related jutsus. We never got to see the inoshikacho casting a nice water style, or frying up some opponents with a nice katon. Kiba was never allowed to slice and dice some opponents with a nice fuuton: wind cutter technique or anything like that. The databook said Hinata had fire and lightning, but when have we ever seen her fry someone with a nice raiton?
See what I mean?
Meanwhile, a certain clan in question has eyes that give them
many diverse abilities such as:
The ability to copy almost any ninjutsu, taijutsu, and genjutsu (and they can do this in seconds even if it took the original jutsu caster years to learn).
The ability to cast genjutsu, which covers several types of feats such as the ability to control someone's movements/actions and just outright make them do whatever you want them to do, to paralyze someone or put them to sleep, to look into someone's memories to gain information, to force a person to talk and reveal stuff, to make a person see/experience false illusions/experiences, to alter an opponent's sense of time, etc...
Precognition that can help them dodge things moving a speeds such as that of sound and perhaps even light.
The ability to rewrite death itself and turn it into an illusion!
The ability to put someone in an illusionary temporal loop until they change their ways!
All of the above stuff just covers the base form of said eye too! This eye can advance into a more powerful form that grants a wide variety of abilities that vary from user to user. Such abilities include:
Being able to incinerate an opponent to ashes by merely glancing at them!
Being able to teleport, turn intangible, and warp things from a distance (including body parts such as the head)
Being able to put a person within an illusion where you can control time and space and make them go through days of torture while only a moment passes in the real world.
Being able to summon an enormous chakara construct that can slice up mountain ranges and even fly!
Being able to issue direct orders to people that are apparently strong enough to break edo tensei's control, or being able to manipulate someone's thoughts and make that person think that those thoughts are their own.
Being able to telekinetically manipulate objects.
Etc...
I also mentioned this earlier, but this eye can even control tailed beasts and turn them into summons!
Reincarnations of a certain individual can advance it even beyond this to awaken an even more powerful eye!
To make matters even more unfair, members of this clan were never even restricted from branching out from clan techniques by Kishimoto. We have seen several non-KKG techniques from this clan such as:
chidori/variants other raiton jutsus
advanced genjutsu (without the use of eyes)
chakara enhanced strength
fire styles
water styles
mastery of the body flicker (to the point where one member of the clan became renowned for it)
advanced summons (snakes, hawks, crows)
etc...
But wait there's more....
Members of this clan don't even have to train to get these eyes! They just have to experience the right emotions! Other clans (with their one weak little jutsu) have to train to master that jutsu and come up with pathetic variations of the same darn thing. Members of this clan don't have to train to awaken their eyes however.
Do you get my point?
Other clans have to train their whole lives to learn and master one weak and limited jutsu, while the Uchihas are gifted weapons to conquer the world in the form of eyeballs, solely because of genes! No training necessary (I'm not saying that Uchihas never train. I'm just saying that their eyes grant them massive "no training necessary" autonomous power). Then they are allowed to branch out on top of that!
Are you really going to sit here and deny the massive advantage that Uchihas are given just because of genetics? And then are you really going to say that it's unfair for people who weren't born with "nuclear world dominating eyeballs" to need a little help in gaining power?!