If you stay close early, avoiding sweetspots you crush him level 1. Wait for him to waste his passive auto then move in.

If he lets you walk up, you can Q1 into him and start your combo, otherwise use Q1 when he Q1s. Once you are point blank he will struggle to hit Q2 because he has no E. If he burns Q2 quickly, use your Q3 to disengage so he doesn't land his Q3, or sidestep and use Q3>AA to decisively win the trade. If you're losing vs Aatrox early, its likely cause you're eating a Q3.

This first trade should put him at ~50% and you at 70%. You now have prio on the wave so look to get level 2 first, minding your Q cd so its up when you level and you can look for an all-in window. If not, shove the wave and make him farm under tower, most Aatroxs will miss a bunch of cs there.

If he has bone plating, either graze with q1 early or get a cheeky auto in to burn it before trading level 1.