Maybe its because i'm not on here everyday, but for me its definitely the sanji fanbase. The discussion forums are constantly flooded with new threads looking for and justifying sanji feats. Even worse is when you step in to have a discussion, I've come across a lot of times where the people who made those threads already have their minds made up, and the only reason they make those threads is to fish and farm for W points to stroke their own ego and make themselves feel better. And the moment someone voices their different opinion or doesn't follow the chorus or play by the playbook, they immediately get challenged and many times even insulted just to shut them down so to not disrupt their own insecure bubble and continue on with the praise and party.
I don't consider myself a Zoro fanboy (of the Monster Trio I think I still like Luffy the most), but even as toxic as the Zoro fanbase are known for, even they aren't in my opinion as toxic or as bad as the sanji fanbase. In the Sanji fanbase it can get to the point of being nuclear radiation levels of toxic. I've seen and met people in the sanji fanbase who won't let people off the hook for disagreeing with them, so they resort to bullying and insults just to kick those people who don't agree with them down a peg for no reason other than to stroke their own ego and to make themselves feel better.
Thankfully, the sanji fanbase here aren't as bad as it was on Orojackson Forums.
On that forum, there was a sanji fanboy, AKA Nessos who was so toxic, that because he couldn't win an argument-he resorts to making a new thread to bring in new people to continue the argument to get back at them- all the while distorting the facts and changing it to his narrative just to win some likes. he also brought me back into the discussion by tagging me and proceeded to make lies just so he can make himself look good.
Bullying, insulting, lying, cheating- just the absolute worst.
After that someone reported him to the mods and he got banned because he was being too disrespectful and aggressive and just refuses to let people off the hook. Some time later i think he also got banned permanently, because his account got removed/locked and you could only see his posts and nothing on his profile. After that he joined Thriller Bark Forums as a mod, before also joining WorstGen.
Whatever toxic Zoro fans are out there, i've yet to meet a person who is as bad as the person i have described above.^ At least the Zoro fans aren't trapping and attacking innocent people and bystanders who are fanboys of neither.