I played in NA, EUW, KR, and APAC servers and to me nothing beats EUW server.
The moment one person gets pissed in the lobby you'll start hearing arabic slurs towards your mom. Like "you're mom is my sex slave sova". Or some slav dude will say "ur dog". And if you ask if he's russian he will answer, "no fuk russia I am from slovenia" with a thick russian accent. If you play london and u have a funny accent they will say "speak english properly" and mock your accent. I swear 50% of people or more who use mic are arabic on every server that's not london.
NA atleast they don't target your parents, they stick to insults like "you're fucking dogwater". NA has some nice people ngl, and if you're an NA player and think that's not true, try playing EU servers. Sometimes you have really nerd ass typical american boys with a super nasally voice who play KJ, plays postplant on a 4v2 and flames u for dying on site.
APAC is the same as NA.
Korea server people try to stay polite but when someone crosses the line all hell breaks loose and insulting your mom becomes fair game. Problem is people don't fucking use their mic. And sometimes there's jaemins who talk shit and type but won't open mic because he doesn't want to expose his kid voice.