Marvel's Guardians of the Galaxy

This is one of the more annoying achievements since Charged Shot is pretty awkward and inconvenient to use, especially when you need to use it quickly.

First, you'll need to purchase/craft Charged Shot from a workbench when you have enough parts (this will be introduced near the end of Chapter 1). Once you create the Charged Shot perk, you can double tap and hold  to charge up a shot, then release to shoot, doing moderate damage.

With that perk available, you then need to Stagger an enemy, who either already has their health lowered significantly or you can try to do so after they're Staggered, and then charge up a Charged Shot and finish them off with it. Enemies typically only stay Staggered for five seconds, and it takes a couple seconds to charge up a Charged Shot, making it pretty tight timing to contribute towards this achievement. As a result, you should focus on this as soon as possible unless you want to just grind it out (more on that below).

By far, in my opinion, the easiest way to work on this achievement is to make use of Quill's Eye of the Hurricane ability where he throws grenades around him. These automatically stagger all normal enemies they hit. On top of that, many enemies also take enough damage from the grenades such that a Charged Shot will kill them. When you land, you then have enough time to finish at least one enemy with a Charged Shot, or two if you're good at using Charged Shot. Pretty much every combat encounter that would start, I would dash into the starting group of 2-4 enemies, use Eye of the Hurricane, and get one or two kills towards this achievement.

You can, however, grind this out in a single combat encounter if you just want to get it out of the way. Use the approach I mentioned above (charge into a group of enemies, use your grenades to stagger them all, then use Charged Shot on one or two), then load your last checkpoint to start the fight over and repeat until you unlock this achievement.