Raisin' Brann

If your brann is too high lvl to die, select dps spec for him and choose "Rage filled Idol" as combat curio, it will damage him for 3% hp/sec in combat
in addition to aggro he should die fast :)

This is very easy to do in the [zone=14999] when the "Precious Ores" story line is active. (story lines change daily, so at most you have to wait 3 days to get this one)

There is a railroad track with mine carts that are constantly running down the track. These carts will cause anything (you/Brann/mobs) to take damage if you get run over.

Just position Brann on the track and have him get hit by the cart over and over until he's eventually unconscious. Be aware that he may occasionally heal. That makes it a little annoying but it's a reliable way to get the achievement without just hoping he'll die in combat.

Rage relic = Achievement completed.