I would never want to hurt or kill someone's pet - but the woman who lives across the street from me was regularly letting one of her dogs outside, and it would run across the street and into my yard.
She kept claiming 'oh, he won't hurt anyone' - but he sure AF didn't look friendly when he ran up on my wife or my 5 year old son. I chased it off a few times, took my dogs out to urinate along the property line a few times, but it would keep coming over. I threw coffee on it one morning when it came up to me as I was getting into my car (it wasn't that hot).
I finally left a message on her door to tell her that, while I didn't want to have to get animal control involved, that she needed to start keeping the dog away from my house and family or I wouldn't have a choice. She kept it under control for a little while, but then went back to letting it run free - t came up on me again in my driveway, and I pulled out a crowbar - but she came running out to get him (I hid the crowbar behind my back).
Finally, I got a call at work one day - my wife had been out front washing one of our dogs (a 90# white lab/pit bull mix) when the woman let her dog loose - and it came running towards our yard. She said 'f**k it', and let our dog loose. The neighbors dog took one look at him and started running the other way - just as the lady came running out to call him back - our dog wasn't having any of it - and ran up on her.
Now, he's a really friendly dog - and wouldn't hurt anyone either (unless they were a threat), but he put the fear of god into this woman. She turned and cowered, and he stopped. She got to find out what it feels like to have a dog run up on you with no idea wtf it might do - since then we haven't had any problems.
If it starts up again, I'm just going to call animal control and deal with it once and for all before either me or my dog have to kill hers.