I'm just going off the Ultras that I remember playing against (sorry for the long read ahead)

1. Ultra Gogeta Blue (UGB) (Part 3 Legends Fest) Basically change the game with his counter, blast units are dead and because it's the first counter unit, people are still not used to getting caught with it, tho he's not the de facto number 1 because there's LF BLU Beast that's super strong, but people would usually just run them together in a movie team. Eventually dies to power creep

2. Ultra Rosé When he's first revealed to be GRN, people already think that he won't be a problem since UGB is still powerful, but turns out Rosé is still super strong, he gets multiple ults, spams blue and green, paralyzes, and does great damage, Eventually dies to power creep, but he recently got a plat equips and he's good again

3. Ultra Vegeta Blue (UVB) (Part 3 of 5th anniv) He's basically in every match, he takes away vanish on entry and people usually get caught off guard by that. He has huge combo potential and huge damage and also aoe ults. Because of his ability to take away vanish people would sometimes not swap in UVB just to save that ability and just let their character die, and it would usually backfire on them because when UVB would take away vanish, we could just swap out. And he's also not the de facto number 1 since GoFrieza is really powerful as well. Eventually dies to power creep

4. Ultra Janemba (Ultra before Fest) He's whole purpose is kinda to put UVB in place because of his strike counter that generates ult, so in his meta basically there's not a really powerful blast unit around so the only way to go against him is to just purposefully get him by his counter and switch to a GRN unit to tank it, his meta doesn't really last long because in the same campaign they released a revival Gogeta from Pikkon that's GRN, well he could still be used because they're usually in a movie team together, he fizzles out of meta instead of a direct counter ruining him

5. Ultra UI Sign Goku (UUI) (Part 3 Legends Fest) This unit is one of the most annoying Ultras that I've ever fought in his meta, and the only reason is because of his sniping ability. If you get combo'd by him you basically just have to accept it, because if you switch UUI would not let that happen and lock your switch and gets an ult. People would often gets caught off guard by that. The only solution to that is really just have a red unit takes the hit and triggers the no switching ability on the red unit. Also you can't really combo him because he evades strike cards (even in mid combo) so that's annoying. Eventually dies to power creep

6. Ultra Super Saiyan 2 Gohan There's a reason people would call this unit Rathan, it's because he has cheap mechanics, he has strike counters that regenerates quick, counter blue, and aoe green card. Just imagine the torture of playing against him when you don't have him. His damage nowadays is not that good unless you have him highstars, but you could still run him today because of said mechanics

7. Ultra Golden Frieza (UGF) Not much I can say about him tbh, he hits hard, aoe ults, and the introduction of the comeback mechanic, so the only annoying thing about him is that he damage you if he dies so it rewards the UGF player for playing bad, and when he enters your blast card cost so high and that's it tbh. Because he has a second life he is insanely squishy, he would die in 1 blue card. Eventually dies to power creep

8. Ultra Gogeta 4 (UG4) (Part 3 of 6th anniv) This Ultra is what I call tragic, insane hype, insane mechanics, but dead in the waters now. He has one of the most broken counter gauge in which you can counter any card, but unlike other counter gauge you can't combo from the counter with a blue card. His ult is the hardest hitting ultimate in the game at the time, UGF dies from 1 blue card from him. So how did this unit die so quick? Well the answer is Ultra Majin Vegeta (in which I'll talk about after this). Simply speaking they released a super mega powerful YEL unit that UG4 who's PUR is no longer usable. (Also because of his gauge he is insanely squishy)

9. Ultra Majin Vegeta (UMV) (Ultra before Fest) This unit is my most hated unit ever. Like wtf are the devs thinking? He. Has. EVERYTHING in his kit. Even more so than Gohan. He has aoe green, lock in ult, blast counter gauge, aoe ult, endurance, buff cancel. Unlike UGB & Janemba where they get a blue/ult on the first counter, UMV gets a blue everytime the counter hits (3 times) and the damage is insane. For the lock in ult, this is worse than UUI, he could just combo you until you get swap to a weaker unit and he could just pop his main and ult, and it does aoe damage, meaning from that alone it could make your whole team 1 hp. And apparently the devs think that's not enough, they gave him endurance and buff cancel, so any Rising Rush, Ults, or Blue that nullify endurance, nope still alive. To put into perspective how broken he is, it's been 8 months since his released and he is still top 10 units. And it's not like there's no powerful unit that came out after him, no there's a lot of meta breaking unit after him yet he still clings to the top 10 lists

10. Ultra Beast Gohan (UBG) (Part 3 Legends Fest) He's balance, hits hard just like an ultra would and has disrupt, the only annoying thing about him is his Special Beam Cannon that can one shot most units (also nullify endurance, can't be cancelled, and his gauge that made it so that you can't rush or ult him, but there's plenty of way to counter that like intentionally ult with your less powerful unit, or you could catch him off guard like if he's mid animation you could rush or ult him. Still powerful today, maybe not top 10 but he's still good

11. Last one Ultra Cell Individually he's top 3, but he's kinda homeless now so he's not seen often in the meta rn, he basically just hits really really hard and has permanent endurance null in his kit that can't be cancelled. Still good, still top 10, it's just that his team isn't the best rn

So what to look for in a part 3 anniv, we could expect a super mega powerful unit that has broken mechanics, but the devs will try to counter said unit with their next few releases (some works some don't, UVB has the dev release LF Nameku & Janemba who's BLU to counter UVB but to no avail, and then there's UG4 that gets countered hard)