Acamarians are a humanoid species native to Acamar III. They looked similar to humans except for an indentation on their foreheads and traditional facial tattoos. Their blood comprised of an iron and copper base, a rarity among species in that area of the galaxy.
Acamarians had traditional inter-clan feuds that could last for centuries, but by 2366 Acamarian society was peaceful. The one exception to this peace was a splinter group known as the Gatherers. Gatherers were known to raid passing starships. With the intervention of Captain Jean-Luc Picard the Gatherers were reunited with Acamarian society. (TNG episode: "The Vengeance Factor")
Later that year, after the invasion, an Acamarian refugee ship became embroiled in a battle with a Betelgeusian starship. The USS Enterprise-E became involved in the battle and suffered casualties. (DTI novel: Watching the Clock)
The devastation of their planet by the Borg led to some Acamarians abandoning their previously peaceful ways. S'hirethal Verauk, then first officer of the USS Rochambeau, lost her husband and seven children on Acamar III, and she became an outspoken hawk, arguing that the Federation had failed to prepare to protect its citizens and would need to take aggressive steps against all potential threats. (ST - The Fall novel: Peaceable Kingdoms)
Despite Picard's efforts various inter-clan feuds continued to flare up on occasion as late as 2409. One such dispute, over resources, required outside intervention from a passing starship to resolve. Then a Tal Shiar fleet arrived, annoyed that the dispute they had created to sow discord had been resolved, and was destroyed by the starship and the Acamarian clans' vessels. (STO mission: "Acamar System Patrol")