Overload Captains are a variant of the Fallen Captain enemy in Destiny 2. They are incredibly annoying, and you need a particular tool to kill them. The problem with Overload Captains is that if you don’t have the right tool, they are pretty much impossible to kill. They will heal back any damage you manage to do them, and it can be very frustrating if you are not sure what to do. You may have run into them for the first time during a Daily Bunker Buster run.
What you will need is an Overload Rounds Mod from your Seasonal Artifact. These mods can be equipped to certain weapons, allowing you to counter the Overload enemies, such as the Captains.
You will need to level up your Seasonal Artifact, then purchase the mod from the first tier that becomes available. You can level up the Artifact just by playing the game, the same way you level up your character. You can get an Overload Rounds Mod for SMGs, and Hand Cannons. Pick the one that suits your own preferences, or grab both if you like, and have enough points.
When you get the mod, go into your Inventory and pick a suitable weapon to attach the mod to. The weapon will now interfere with the Overload Captain’s abilities. Enough damage from the weapon will disrupt and stagger an Overload Captain, meaning they cannot teleport or heal. When they are staggered, it is easy to switch to your Power weapon as they cannot dodge, or even move. Do as much damage as you can, then switch back to the weapon with the Overload Rounds and stagger them again before they have a chance to heal the damage.
These enemies also have substantial health bars, so be sure you take out all the smaller enemies that are with them first, so you can focus them down when it’s and one versus one fight.