Deadeye Achievement in Halo Infinite
Earn 3 stars in a Weapon Drill.
The first Needler challenge is easy to do because the needles reach the target automatically and the enemy explode (it looks like they need more than the 7 needles from previous games).
Shoot 15 needles on each enemy if 2 of them are close, reload when you aim at another enemy, rinse and repeat. And shoot even when the timer ends. You may not get it on first try but on second try you will know where enemies will appear.