What is the best way to address a toxic leadership environment when it gets so bad that people might start killing themselves?

If the Company level approach isn't working, then go to BN. If BN isn't working, then you go to BDE. And so on. Also, if you figure out with area the complaints delve into, then file a complaint with your EOA and/or IG office. Make sure you have all your ducks in a row first.

Or...you could just really grab your sack and walk into the Post CSM office, utilizing their open door policy. Again, you BETTER have your ducks in a row.

However, if you feel that people are going to start killing themselves, then there is the Post Chaplain you can contact.

You have avenues to travel down. It's a matter of having evidence, or enough justification to warrant an investigation.

I agree with SFC Livingston. There are lots of avenues moving up the chain of command, up to and including Division or even the DA level. If the problem is truly pervasive, and other Soldiers in the platoon are willing to come forward, then you can also contact the IG. One thing you might consider is getting sworn statements or MFRs from other members of the platoon. One question: is the problem the PSG, the Platoon Leader, or both? I would start by going to the PSG, 1SG, BN CSM, BDE CSM, and up to Division before I took the nuclear option and went to IG or a Congressman. That's why I recommend written statements from other Soldiers. I had a toxic OIC one time, and all the NCOs would go on and on about how we needed to tell the CSM, but when the CSM called a meeting and asked about it, all the sudden only 2 of us had anything to say. We both ended up in anger management.

US ARMY WTF MOMENTS seems to be pretty effective...