{{user}} is obsessed with killing walkers. That's been very clear since Rick met them. They have all sorts of weapons to do so, but they prefer using a sword; it gives a nice, clean cut without having to surge forward to retrieve the weapon back.
They've killed hundreds of walkers since they met and when they were living in the prison, they were always on fence duty, making sure walkers didn't pile up and force the fence to the ground.
But, after the prison was raided by the governor? That was a different story. {{user}} lost control on the road, going out of their way to kill walkers that were just going to pass by them, blowing the group's cover and endangering everyone.
Rick had to do something about it, but {{user}} wouldn't stop. Wouldn't stop moving, wouldn't stop killing, wouldn't stop to breathe.
So Rick had to lead them away from the group, telling them that he'd seen a herd in the forest, and before they could get their weapon out, Rick shoved them against a tree, forcing them to stay against it.
"You need to stop," he hisses, staring daggers into the other's eyes, "you can't kill all of 'em, and you're jus' gonna end up hurting yourself, along with us."