I have experienced that most low Plat players tend to be toxic and verbal abuse, they are so full of themselves, they blame other players for everything. In one of my most recent matches I got matched with Season 6 platinum V player who is, at the time of writing this, Silver 3. He/she (probably he, because of behaviour) played J4 in jungle, refused to communicate, didn't use pings, stayed after gank on lanes and waited for last hit on minions, but played good in teamfights. We were dominating at that point, we destroyed inhib and both nexus turrets and got nexus to half hp. Then we decided to go back, but he and top laner (Darius) stood there waiting for enemies. they made a 2 man ambush in jungle without full hp. They of course failed and died.
This is the point when J4 started flaming and raging on us who backed for doing so. Next fight was lost because out support (Thresh, just a bad player or bad day) went too far and died. I tried to POLITELY explain to my team that we should keep under turret. But J4 jumped into 5 enemies without pinging or saying anything, killed carry with all his abilities and died instantly, then we were left 4v3 and J4 was strongest in our team. Because our top laner was always with J4 he went in too, but after couple of seconds and died. I (Katarina) was left alone under second turret on mid, and adc (Jhin) was aside ulting. They easily killed us both and pushed all the way to nexus turrets on top and mid. We all respawned and J4 told us all to go to top river, and we did. Everyone in their team was alive at the moment. We were supposed to have teamfight at baron because we knew they had wards there and because we knew we were stronger. But that's only what I though J4 had in mind, instead he and Darius attacked baron while we were trying to push enemies away. Baron got to 2/3 of health really fast, so I moved a bit towards baron to throw some spells, J4 and Darius suddenly stopped attacking it and started to back away. that's when their jungler (Lee Sin) ulted and knocked three of us in the air, making it perfect for enemy mid laner (Yasuo) to ult. That's when we lost the fight and the game. J4 of course flamed us all for being useless and weak, but he made the wrong call.
In game summary screen the continued to flame us all, mostly me and support for being useless, he started griefing, invited everyone to go 1v1, he though that he was best in the game because he dealt the most damage, not realizing he threw a win.
And don't think that I did everything perfectly, I had some fails here and there, but they weren't as important as his.
That's just a game that I recall the best, there are many of these players in The Fields of Justice.