The way that I see things, there are three things that I feel definitely should get banned:
1. Palafin
This guy is busted, straight up. He constricts the way you have to play in a very overwhelming manner. With very few checks and only one counter (Dondozo), he can switch into a LOT even though his ability does force you to spend two turns switching. These turns can still be used effectively in order to not lose momentum, and Jet Punch is absurdly strong. I do wonder if Jet Punch could be part of the issue- I'm not advocating for a JP ban, but if he had to rely on Aqua Jet instead, I think he definitely approaches the realm of reasonable.
2. Bundle
Bundle's incredible speed stat outspeeds everything but Dragapult, a mon that doesn't check Bundle, unboosted. Bundle almost forces you to run Scarf, as even Pokemon that resist Bundle struggle greatly to switch into a Hydro Pump, AND the bird finds ample opportunities to switch into physical mons with a defense stat that, while not great, allows it to live hits you probably wouldn't expect it to.
For me, at the current state of the meta, I find that mons that are overwhelming without needing or regarding Tera to be the mons we need to keep on the radar, and both of these mons fulfill that criteria more than any others in the meta.
Finally, I am most definitely on the "Ban Tera" train. I don't think that we can reach a stable metagame with Tera; while I absolutely love the creativity that can be used with tera typing, in my eyes it makes the meta game incredibly difficult for newcomers to enter as there are just so many different things to have to be considered on top of the inherent complexity of Pokemon that draws people to competitive play in the first place. Maybe my perspective isn't the right way to decide whether or not a generation-defining mechanic should be banned (in fact, I don't think it is at all), but I think that it's an important perspective to be considered.