Enemies that aren't regular ones can be recognized by their health bars:
- Red bar is for normal enemies;
- Orange represents Elite units that usually look like an upgraded version of the "regular" ones - and that is usually the case - besides their shield or greater endurance they don't differ from other, more massive enemies;
- Yellow indicates that you fight a boss. Here, you must be prepared for bigger problems and that an enemy can often have abilities that are beyond the usual ones.
If you face a mini-boss that leads a small group then you should start that battle by eliminating the weakest enemies, such as robots. They are killed with 1-2 shots but they deal similar damage to other enemies.
During final boss fights you should try to eliminate them as fast as you can, especially from a distance. Reason for that? If you defeat a main boss then other enemies in the area will disappear. However, there are moments during missions when you can't eliminate a main enemy without performing specific actions or getting rid of their minions (e.g. when they give a boss protection in a form of indestructible shield).