Help Me Improve

I have a group that I need help to improve.

An incident happened where a member said "miserable %%%% kys". This member is one of those trolls who have no intentions. If you knew him, he is a good guy. However the words "kys" is a bit strong to my tasting. And considering the purpose of League's Club is "meant to be the most toxic free League environment" I don't think it would be proper to let this slide. I don't intend on banning him. I just want to alter the rules, which need to be updated anyways. So my question to you all, the League community, what are some words you hate to see no matter how nice the person is? What are some words that should be "banned"?