Okay history lesson
She's had antis since the beginning because her roommate attracted mentally ill hambeasts and trannies from /cgl/. She used to have a literal, actual stalker who basically tried to groom gaijin idols, getting them to Japan and then trying to play sugardaddy and harassing them if they don't suck his fatfuck pedophile dick. He spread rumors on a schizoblog and also manipulated her managers with fake news till she was fired (this was why her idol career ended, why she was so depressed until finding hololive etc.) He's harassed multiple gaijin idols like this but Kiara got the worst of it, basically. Anyway, people picked up the rrats from the pedophile stalker about her roommate basically.
Her starting weeks were also genuinely awful so she rubbed the majority the wrong way, even putting aside the rrats.
After she fixed her shit and improved her streams, the hate subsided and she started being accepted in the threads and growing a fanbase, starting the gigastacy meme etc., the threads during her streams started being fully positive without anti noise, people even started talked about how her antis left the threads and the general sentiment was that she isn't hated anymore (this was around October last year)
In hindsight all of this wasn't that signficant compared to nowadays full-blown obsessed schizo antis. (Ame, Mori and Gura all had periods of hate or at least obsessively shitposting samefag antis similar to that.) The current situation is a different beast.
Anyway, the anti wave resurged at the start of November. I believe it was the art stream where she drew Pekora that started it, it really got the narrative going that Kiara is "creepy". Lots of seething /hlg/ dogfuckers came out of the woodworks because they resent her for being a gaijin waito piggu that's fucking their oshis. This coincided with the infamous Subaru stalker narrative spread on 5ch just a few days later, so naturally the EOPs from /hlg/ absolutely ran with it.
Finally we had the Pekora Kiara collab near the end of November and this made the SEAniggers join in on the hate and essentially team up with the dogfuckers. So the antis were effectively multiplied by 2 in sheer numbers, and it absolutely EXPLODED, threads were absolutely flooded with shitposting and obsession. Here's also where the whole "Kiara is fake/manipulative etc." rrats started, the SEAniggers came up with this originally to find ways to discredit the collab because it was successful (example being trying to make Kiara crying look creepy because EOPs didn't have subs yet).
Well, the hate never really subsided from that point on. Famously, when holoID gen 2 graduated they couldn't stop talking about Kiara in the sticky for some reason and her name literally reached 1000+ mentions. I think the SEAnigger faction of Kiara antis actually heavily outnumbered the rest in the end, because every fucking anti post was with broken English. And the anti posting would always spike extremely during SEAnigger hours, it was very obvious how it came and went in waves. Though obviously, lots of antis attract even more antis, especially if they actually swallow rrats, so a snowball effect also happens.
Famous was that one guy endlessly samefag-falseflagging (literally like 12+ posts) as a KFP posting shit along the lines of "Kiara gonna surpass Gura hurrdurr" and then replying to himself with "why are chickenfags like this". He got banned and all posts from his IP deleted which exposed the whole thing, there's a screencap.
I stopped browsing the threads regularly a few months ago due to starting wageslavery again, so I dunno how it developed since then. It seems like antis just timelooped back to old doxxfaggotry now? I do think the majority of anti posts you see on this board are from a few mentally ill obsessed schizos. Anyway the most important thing to remember is that when the anti tells you some "reason" that ORANGE WOMAN BAD, they are lying 99% of the time and are actually just a seething SEAnig or dogfucker who became obsessed for one of the reasons mentioned here. For instance literally nobody gives a shit that Noel's roommate did actual porn (not a rrat). These things are never what drives an anti, lmao, they just use it to seem legitimate instead of like obsessed schizos who lost their minds over imagined nothingburgers (I guess on some level they are still self-aware), which they in fact are.