Greninja... Mach Punch and dead. I mean you can kill it with everything, All common scarfers kill it. It's not Uber.
Deoxys-A is more frail than Greninja. It loses to Shadow Sneak spiritomb, infact all Deoxys do, why are they uber?
Mach Punch isnt a good argument and thats ignoring the fact that Greninja, can you know, change types so its not even super effective anymore. :\
Really... Just notice the difference between them.
Not everything has to be the level of mega mence or mega ray to be classed as "uber". If a pokemon is broken in standard play, it will be banned. End of. Even if it sucks in ubers but is still too much for ou.
Also, using scarfers/revenge killers to get rid of something solely should tell you how broken something really is. If you have to resort to
revenge killing something to stop it (thus probably foddering your whole team because none of those scarfers can switch in directly so arent even checks), uhhhhhhh isnt that indicative of a MASSIVE problem with said threat?
Lastly ill address "it cant wall break because 95/103 offenses are mediocre" and "Gunk Sot and Low Kick dont beat its counters". 95/103 offenses maybe "mediocre" when we have megas running around but you are all simply underestimating the fact that it gets STAB on everything, that is a HUGE 50% boost to all its moves. Ill give an example.
40 Atk Life Orb Protean Greninja Low Kick (60 BP) vs. 4 HP / 252+ Def Eviolite Chansey: 221-265 (34.4 - 41.2%) -- guaranteed 3HKO
Without STAB that isnt breaking Chansey. But with Protean and Stealth Rock present, that is ridiculously close, infact 2hkoing some of the time.
Protean is why its such a good wall breaker and in my opinion would a better case for banning this ability rather than Gren itself who would be more manageable without it.
Also its speed is ridiculous and it outspeeds basically all of the metagame.
EDIT:
Rotom-W also isnt a counter.
252 SpA Life Orb Protean Greninja Extrasensory/Dark Pulse vs. 252 HP / 0 SpD Rotom-W: 136-161 (44.7 - 52.9%) -- guaranteed 3HKO after Leftovers recovery, 2hko with Rocks.
40 Atk Life Orb Protean Greninja Gunk Shot vs. 252 HP / 0 Def Rotom-W: 160-188 (52.6 - 61.8%) -- 98.4% chance to 2HKO after Leftovers recovery, 2hko with Rocks.
Rotom-W cant take and is generally inept at taking hits from both sides of the spectrum, js.
Its counters are niche pokemon like Gastrodon who is probably the best example of one this thing has and that is ONLY because no one uses Grass Knot/HP Grass anymore lol. Same with MegaSaur and Extrasensory, which brings me to my next point. Its ridiculously unpredictable and has a huge movepool, finding out which moves it has and doesnt pack will probably cost you a pokemon to find out. Salamence was banned in gen 4 for this reason.
Also as of note it can set up Spikes and KEEP them up thanks to it wrecking defoggers and spinners with offensive pressure. I dont think i need to say why that is retardedly dangerous.