Therapy and medication. That's the only resource that I know works.

I will tell you what has worked for some of my clients. YMMV.

Don't think of an elephant.

You may not have been thinking of an elephant before that order was given, but it is impossible not to now.

Also, it's not the thought that's distressing, it's your reaction to the thought.

Imagine that you get an intrusive thought about killing your neighbor. You react to this thought by trying to suppress it. Now you are focusing your full attention on this thought. Now you are frustrated because you can't stop thinking about it. It gets worse and worse

You are dealing with 2 different resistance focuses. The first is the act of committing violence, the second is the THOUGHT of the act of committing violence.

It is a relative simple thing to prevent committing the act. There are many barriers to killing. Not the least of which, I hope, is your personal morality.

The thought is different, the harder you fight it, the more powerful it gets. Does that make sense?

So instead of fighting it, accept it.

Accept that you have had this thought. Trust that just because you have this thought does not mean you're going to act on it. If you didn't have enough self control to stop yourself from obeying every random thought that pops into your head, you would surely be in prison now.

The ramp up only comes because you are putting so much energy and anxiety into making yourself stop thinking about it. When it doesn't work... You put more energy and anxiety into it. Now you're getting more frustrated and believe that you can not stop the thought, which increases the anxiety and frustration.

So stop fighting with it. Just let it be there. It will vanish if you try to focus on it with curiosity instead of fear and frustration.