More severe offenses may result in skipping punishment tiers. If it was for chat related offenses, it usually boils down to things such as homophobic or racial slurs and other hate speech, and death or suicide threats. If the offense was gameplay related or out-of-game harassment or exploits then an immediate ban is normal. Resuming toxic behavior after this ban is up may easily result in a permanent account ban.
What the other players did or said does not justify the actions of anyone else; retaliating with toxic behavior just means you're both toxic. Instead of responding in kind and making the situation worse, please just mute and report them. They will be judged for their own actions regardless of whether you responded or not, so you're only putting yourself at risk when you stoop to their level.
If you want me (or the community) to go over your reform card (if you got one for chat offenses) you can post it here. If you just want to appeal your ban to Riot you need to submit a Support Ticket.