Depends on what you did exactly, however Riot should issue a "Reform Card" or at least provide support to why a player is being banned, you can submit a ticket like I had to a couple of days ago and ask Riot why you are banned.
Thanks for admitting you were rude though, its the first step to actual reform the best thing you can do is mute everyone the moment toxicity starts, don't repeat yourself more than once, and if players start an argument ignore them all in game and play the game this keeps you from saying things you don't want to say back aka hateful comments.
The next step is to learn and understand that League OF Legends is just a game while you play to win as a solo player, is not to take it seriously to the point even in promo series where you actually just go off on everyone for playing badly, or when there are trolls in the game. (In other words play the game to win, but watch your own behavior, don't threaten reports, don't ask others to report.)
In other words play to win the game but understand that if others don't want to listen example playing defense when needed or just flat out give up be like whatever to yourself play the game out report them be done with it, but because players are toxic isn't an excuse to be hateful back in chat and responding will only get you into trouble.
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You know you were wrong but somehow a permaban is too harsh?
It takes a lot of effort for someone to get escalated to a permaban from nothing.
Honestly it doesn't take a lot lot I had a lot of bad games a couple of days ago, haven't had any warnings or chat restrictions since they wiped the clean slate thing, and got a instant perm ban for "Feeding" but really just me having a hard time and doing awful in the matches I was matched with players didn't want to play defensively it made the game very hard.
Other cases where they will perm-ban your account is if you make Real Life threats, or give out other peoples RL information for example will be taken more seriously some game companies like Blizzard even call Law Enforcement.
Although the Terms OF Service, Riot says they don't have to give an answer to you when they ban your account, they should still provide a reason instead of just a code which the user has no idea why they are banned anyways, and a Terms OF Service which I believe there maybe some loop-holes in it itself with certain laws, and it also doesn't prevent users from making smurfs because Riot doesn't actually ban players but for some reason allows users to keep making accounts if they want to to be toxic?