StormRazor suggestion
Storm's Edge: If you haven't attacked in the last 2 to 3 seconds (scaling down with attack speed), your next basic attack will critically strike for** between 125% to **_160% damage (+1% per 1.5% Crit Chance)(max 200%) and _**grant 5% to _10% Movement Speed for 1.75 seconds depending on when you hit _(values weighted more as you near max time). **
by weighted more I mean parabolic-wise. such that at say 2.3 sec its does ~130% dmg and at 2.7 sec it's closer to 151%. Same for MS.
edit tried to make a clean description of how this might read https://imgur.com/a/1jPamfF