[cheebacheeba]

Yes.
That would do it for me.
I've had one dog murdered (albeit a different method) and that dog was sadly enough, an "only friend" in a pretty fucked up time in my life...so yeah, this one would have me kill someone if there were no ramifications but those I'd mentally impose on myself. I'm not afraid to admit, however strange it makes me, that I generally value the life and company of animals more highly than the greater majority of humans.

Your smaller brother/sister/close younger relative of choice goes from soft into heavier drugs.
They say they want to stop but can't control themselves. You agree to help. You confront a dealer who tells you to fuck off, and you're lucky they don't fuck you both up for good measure. You go. You tell the relative not to go back, and they actually don't. One week later they go missing. You don't see them for months.
They have no other enemies or problems. The same dealer makes snide comments like "keep walking, you don't want to wind up missing".

Kill?