So this is true reason why knockups are overpowered
Imagine champ like
he has big radius on his ult, quite small cooldown with items, full AP malphite oneshots you, tanky malphite deals still pretty decent amount of damage but regardless of anything the knockup is still constant neverchanging duration CC
can throw at you thousands of knockups you have to dodge if you are like squishy and not even that his ult extends the CC and gives him more damage so like the fact that he can knockup you more often while there's no counters to knockups is unfair
champ taking almost 0 damage when he ults that can CC chain you very effectively thanks for him having a knockup
Fed cho.... just run away so he can't eat you oh he landed his Q knockup and you didn't dodge so you die because knockups are holding you there for eternity - he has many ways to catch up to you

already busted champ that needs 1 item and 1 out of thousands Q she throws to land on you and your chance to get oneshoted triples, this champ has also a knockup?/knockback whatever unfair
champ that is already busted enough to fight darius with 5 stack bleed has a knockup that is hard to land but knocks you up almost as long as morgana q so basicaly eternity on top of that he can cc you with his W and slow you another knockup in ult I forgot
heh...
one of the only knockups that are fair because the wind up time on that Q takes a long time
's knockup also sounds pretty ballanced like a skillshot you know not like
= instantly dash on that location (going ap oneshots squishies also)
also
's knockup is pretty much ballanced it's used for enemy to fly away or to knock them up for a short time it's ultimate afterall
and no just because some of these knockups are on ults doesn't make them ballanced (lategame 40cdr ultimate hunter and boom you have ult on almost any champ for every single fight)
I won't continue those are already lot of champs that can exploit knockup to their advantage..
Q and
E.