Honestly, I'd love to see Annhilape/Rage Fist (more so Rage Fist) to be nuked. Rage Fist is such a ridiculous move, it's Rage but y'know... Actually good.
Aside from that, I'd point my finger to Tera... But not Tera in general, there's one specific Tera that really stands out from the rest. Tera Normal.
My reasoning for this is that defensively, Normal has only 1 weakness -- Fighting. Everything else is neutral, or in the case of Ghost, ineffective. Offensively, it absolutely makes two specific moves absolutely disgusting; Extreme Speed and Boomburst.
As I'm sure most of you either have played with, or against, Tera Normal E Speed (either in OU or UU!), it just... It's so stupid to deal with. You get a free 120 power +2 Priority move that allows you to outrun other +1 Priority users. If you don't have a Ghost, Ghost Tera, or can't burn the E Speed user, they can keep clicking E Speed.
Boomburst is a different beast altogether. Base 140 power (210 after Tera), ignores Substitute. It's an entirely terrifying move to switch into, unless you're a highly resistant (or immune) SpDef wall. While it isn't a +2 Priority move like E Speed, two major mons that can make use of it (Toxtricity and Noivern) can absolutely run train through teams in the right circumstances.
However, in the case of E Speed, a lot of people will bring up "just use x Steel/Rock types!" The unfortunate problem with that is this: Consider the 3 Pokemon that can make use of E Speed in the game right now; Dragonite, Lucario, and Arcanine. Arcanine is the least threatening because it has 0 reliable ways of getting an Attack increase. Dragonite has Dragon Dance (which also gives speed), and Lucario has Swords Dance. If we look at the argument of using a Steel/Rock, both have access to Earthquake. Lucario and Arcanine have access to Close Combat, but Gholdengo can deny that. However, Lucario and Arcanine both have access to moves like Crunch, Flare Blitz, Flamethrower, Fire Blast, etc.. No matter which way you can twist it, outside of the 4 Move Slot Syndrome, all three have moves that can deal with incoming threats to a Tera Normal E Speed sweep.
My problem with Tera Normal hinges mostly on E Speed, but as someone who's played around with Tera Normal Boomburst, I can't deny its validity. It's an insanely scary thing, and getting hard cheesed by E Speed just leaves a sour taste in my mouth. So much so that I've actually resorted to playing with bulky Talonflame as a physical bulky mon to try and punish E Speed mons.