Question for All

I was reading something about "relational agression" on another board I peruse. So, my question (all in good fun, not to make anyone feel bad or cry) is:

What is the worst, most low down thing another person has done to try to separate or drive a wedge between you & your S/O? What's the most agressive move another person has made to try to ruin or add doubts to your relationship?

Happy

The same girl that ended our friendship over D, actually had a lot of influence with my break up with my ex. I know things weren't the best between me and my ex, but is was fixable and she would feed me thoughts to where I thought my ex was a truly horrible person. Seeing that - at the time - she was my best friend, I listened. I thought maybe she saw something that I didn't. I ended up breaking up with him. Which is good and bad. We really weren't meant for each other, but I broke up with him for the wrong reasons and for the wrong person. I should have done it for me, not for her. I'll never forgive her for that....then she judges me for being happy w/ D. It's sad to think about, but I'm happy it happened, I would have never met D.