So i have a question

Likely because you were isolated and had little armor. All you gotta do is stand near any allied minion/champ/turret and he loses a huge chunk of damage.

if you are alone khazix can do like 40% with one Q but if you near a minon or any sort of ally he does nothing to you

yeah i have done khazix mid and it still hurts because you dont see when your isolated and its not fair from your minons so be careful

Basically a level 6 Kha'zix deals 156 + 156% of bonus ad + an additional 60 + 105% of bonus AD with a single isolated Q, so say Kha'zix has warrior, and probably about 10 AD from runes About 70AD to work with.

About 400 damage from his Q at level 6 his next auto deals 137 + 55 from his passive, so the Q + AA deals just shy of 600 damage not factoring in resistances.

You also have to factor in if he hit you with W and E, which collectively add another 230 damage give or take.

Say you were level 6 lux in mid lane, you're actually dead from the full combo.

Kha'zix is really only weak before 6 and then against tanks afterwards.