Banning Chien-Pao is really not an open and shut case. It's undoubtedly the best offensive mon currently but that doesn´t equal broken. That being said...
1. Most counterplay involves burning your own Tera. While this maybe not be seen as that big of a deal considering that Chien only forces this by burning its own tera, it really is worth noting that this still extremely prediction reliant. Also, all counterplay listed pertains to Tera Dark Chien, Chien can easily nae nae on those answers by Teratyping into another type that is not Dark (that's Tera for you!). Chien is a Tera abuser after all and it is not forced to run Tera Dark to be menacing, it's just that the Meta has not developed that far yet, but trust me, it WILL if we keep it in the tier.
2. Paldean-Tauros is extremely overrated. It is a subpar mon in the OU metagame and it baffles me its being used as an actual argument against the Chien-Pao ban. It IS viable and has a niche, but saying "this OU mon can be handled by an UU/RU mon!" is not the argument you think it is, lmao. Yes I know it coud still rise to OU but I firmly doubt it, and if it does, it's not cause it really fits the Meta, but rather because its niche of checking Chien will become a necessity for some teams (and that just means some Chien Paos will start running Psychic Fangs anyways in the rare case another team member couldn't easily beat Tauros, cuz dealing with Tauros really ain't that hard in OU).
3. Broken checks broken means nothing. Chien checking some other broken shit is the worst argument ever against its ban! "Hurr durr Garg will get out of control!" Ok then we shall ban Garg too! And whatever else spills out of control cuz of the lack of Chien Pao! This has been said a trillion times!
4. "It makes Stall better"? That's great! Stall is in such a rough spot it could really use some help. Are you sure you're listing negatives? Or do you just hate stall so much you're willing to ignore blatant metagame problems just to keep a barely viable strategy nerfed? Why? Stall is not uncompetitive (and if you think it is, you have no idea what uncompetitive is).
5. "But priority!". Not a single relevant priority move OHKOs Chien Pao if it already Terastilized into a pure dark Type, unless said move was already boosted by Swords Dance. The only exceptions are Banded Mach Punch Breloom (who still gets outspeed and OHKOd by Ice Shard without its precious Focus Sash. Tera Fighting Focus Sash could do the trick I guess but that's a suboptimal use of Tera) and Tera Normal ESpeed DNite (only +2 is a guaranteed OHKO, but since Speed is +2 priority move Tera Normal Dragonite only needs to survive one turn to kill Chien since ESpeed is a guaranteed 2OHKO at +0. Although a -1 Tera Normal or a +0 Regular DNite are not 2OHKOing Chien, I don't think that's much of an issue). And remember, this is just regarding the Tera Dark Banded set! (I am excluding Psychic Terrain out of the conversation cuz I can't criticize the use of P-Tauros as an argument and then use Indeedee as MY argument lmao).
However, to be fair, if you predict Chien right, it becomes fairly easy to deal with. Priority can also deal with it swiftly if SOME chip damage was done previously or if the attack is boosted beyond just a Choice Band, and while checking him usually requires you to use your tera, it often involves various viable Pokemon turning into types they already wanted to turn into anyways, like Dondozo Fairy or Dragonite Normal.
That said, even if Chien is banned, the most likely scenario is that it will get retested after Home drops! The dex is really limited right now and answers can be difficult to find, but I have no doubt Chien-Pao will perfectly fit in SV OU after Home drops. I see banning him just as temporary solution. I'm in favor of a BAN and will try to get reqs.
In conclusion: Ciao ciao Chien-Pao, see you after Home drops!