If you are a lot higher ELO than your opponent, don't be an asshole
If you are platnium, diamond, etc... and somehow are matched against and then crush an unranked, fresh to league, player (or someone significantly lower ELO than your's), do not be an asshole about how easy it was for you to beat them. No one is impressed with you or your performance. You had basically a free lane and likely a free win. You don't have to boast in all chat who the better X (lane/role) is, because it obviously was you. You are high ELO, they may have never played against your champion before, or just haven't gotten the hang of everything quite yet. Point is, no one really cares how good you are and you carrying on about it just makes you look like an asshole.
If you feel the need to talk to your opponent, maybe give them some advice (productive/helpful advice, not "uninstall" or "get good").