Khazix still dealing 1k damage per Q

So I just played Garen and it was fun tbh watching my entire team get murdered before I can even reach the Khazix and peel. At one point I remember me chasing after a 20% hp Khazix, the Khazix leaps into my Sona GETS EXHUASTED and proceeds to one shot Sona anyway before I kill him. He was 9/6 at that point, Sona had 1.6k hp. What the fuck? He literally Auto'd, Q and void spiked. He was exhuasted.

The rest of the match was Sivir/Sona getting one shotted while I struggled to even reach the Khazix who was invis inbetween one shotting people.