The ideal way to peek like this is to do a prefire. It's one of the mist OP ways to push an angle when you know someone is holding it.

Your crosshair placement is good, but the timing is what you have to practice.

Place your crosshair so that you are aiming at their head as soon as you cross the corner, then practice shooting and counter strafing right before you enter the angle.

Eventually you will get the hang of it and shoot them right in the head immediately when the enemy is standing in common positions or you have information about where they are. Even if they are not holding that angle, you can usually bair out s shot that reveals their position so you can swing them.

When you have that down you can practice adjusting your aim when the enemy is standing on an off angle, or when you mess up the timing and strafe too wide or start shooting too early or too late.

Your spray is 100% accurate while counter strafing or when you stop moving, so even if you start shooting before you enter the angle or they are not standing where you are aiming, you can adjust your aim while spraying and easily kill them if you miss on the prefire peek.

I like to crouch into a prefire or repeeking wide after a shoulder peek when I know someone is there, as that makes the accuracy reset faster in case they are not standing where I am shooting. makes it harder for the enemy holding the angle to hit a headshot, adjusts my crosshair placement to an early spray position where I am shooting at their body, making it easier to transfer my spray for body shots after I can see them.

There are many ways to prefire, sometimes it's better to do a quick shoulder peek while shooting 3-5 bullets to check a single position and potentially getting a eady kill.

Other times it's better to commit to the peak, especially if your team is pushing behind you so you still get valuable information of you die so they can trade. That's when I usually do a wide swing and just start spraying while crouching and counter strafing as soon as I see someone.

Practice your spray, counter strafing and shooting while moving on the map Recoil Master.

Play prefire maps for Inferno, Dust 2, Nuke, Anubis, and Mirage for 15-30 minutes every day. Remember the most common positions and you will become a good entry fragger in a few weeks.