Disposable Bandits

"[Y]ou can kill smugglers and bandits and other outlaws all you like. Outlaws have no rights. Plenty of adventurers make a living from killing and looting outlaws."

- Arrille, The Elder Scrolls III: Morrowind

Laconic: Bandits as low level enemies with no negative consequences for killing them.

Groups of bandits are very popular picks for the lowest power human(oid) enemies in the Sorting Algorithm of Evil in fantasy fiction. Their motivation is straightforward and requires little explanation, they can come from anywhere, and, while armed combatants, bandits rarely have significant combat skill and generally only have actual training if they began as military deserters (in which case their training is generally still minimal) making them some the weakest combatants possible. Even more importantly is that, unless they style themselves as champions of the poor, bandits have absolutely no legal or social protection and the only people who object to killing bandits are other bandits so the heroes are free to slaughter them as they wish.

If they're stupid enough to try attacking someone who winds up clearly overpowering them, they're Mugging the Monster.

Tabletop Games

 * Very common in Dungeons & Dragons and Pathfinder modules.

Video Games

 * Fights against bandits in early levels are a stable of most Fire Emblem games.
 * Common in The Elder Scrolls. One of the first NPCs the player meets in The Elder Scrolls III: Morrowind even outright tells the player such criminals have no rights under Imperial law.
 * Bandit parties in Mount & Blade are generally the weakest non-civilian party on the world map and, unlike civilians, nothing negative happens if you kill them. After the early game groups of "deserters" start spawning, which are functionally identical except for being stronger fighters.