This takes place in Chapter 9 after leaving Nibelheim
All credit for this guide and video go to PowerPyx guide which I found here:
https://www.powerpyx.com/crisis-core-final-fantasy-vii-reuni...You have to kill all robots at sniping spots without any of them escaping. If you alert them and take too long they will run away after a short time. Aim for the head as it does enough damage to instantly kill all the regular ones. After fully upgrading the rifle you can also aim for their shields as they are easier to hit and the fully upgraded damage still deals good damage plus staggers the robots on each hit. There are no checkpoints during this minigame, if a robot escapes you must reload the last autosave to respawn at the start and redo everything.
1st sniper will have 1 stationary robot.
2nd sniper will have 1 stationary robot.
3rd sniper will have 2 moving robots.
After the 3rd sniper run back and forth to farm kills on normal robots and fully upgrade your sniper rifle before triggering the 4th sniping spot. (Author's note: I think it's around 90-95 points to fully level the sniper, 1-10 with 3 points each, for 3 skills, plus 6 points for the smart bomb upgrade, which I didn't use. Upgrading fully isn't completely necessary but is beneficial and only takes a few minutes extra).
4th sniper will have 3 moving robots in the distance, kill the one on the right first, then left, then middle.
5th sniper requires going right at the split in the road, it has 3 stationary robots that you can instantly kill by shooting the barrel.
6th sniper is down the road on the left with 2 boss robots: BIGGS and WEDGE, who have 9999 HP each. With a fully upgraded rifle it will take 3 headshots to kill one, and you can simply fire a smart bomb to kill the other one.
7th sniper is at the next split on the left with 3 robots. Quickly kill them before they retreat, with fully upgraded damage you can simply shoot their shields which staggers them but still kills them quickly (this is easier than trying headshots and missing).
8th sniper is the final one, it’s when you follow the road to the right. Shoot the barrel near the left robot, then headshot the other two or just shoot their shields quickly. If they try to retreat, you may be able to hit the barrel to stop them.
Continue to the end of the section and the trophy will pop before the next save point.
Video for those who prefer: