Charged abilities (eg. Vi Q, Varus Q and Xerath Q) make my ping spike really hard.
I was playing a ranked, and as soon as I hit 3 I skill-up my Q as Vi. The first time I cast it I lagged really bad but I thought it was just a random lag spike. I then tried to gank mid and as I charged my Q I completely lagged out. (Ping went from 80 to 1000) I got pretty irritated as every single time I used my Q I lagged out. Later that month I had to re-install windows and therefor re-install League too. I played another game with Vi after that and had the same problem. So that ruled out the option of it being a broken file or something like that. Later that week I picked Xerath and I noticed that my Q made me lag out the same whay Vi's Q made me lag out. So I knew it was a problem with the charged skillshots ( I tested Varus in a custom and the same thing occurred). (Video might still be uploading)