Since they've decided to let you go instead of him, it's unlikely they will take anything you have to say seriously, until you back it up with similar reviews by other people he has managed or interacted with.

Although the other comments mention letting it go, I would suggest not to. The only thing needed for evil to succeed is for good people to do nothing about it.

If you work hard enough bringing out proofs of his toxicity - even to the employees and the future people who will work under him, I can say for granted something is bound to happen to him. I know this because I have done so with reasonable success in the past. Here's my story, if you're interested.

I joined a startup I was excited as hell about, and had the happiest times of my life for the first 1 year. It was a win-win - they loved me and I loved them. However, once it went profitable, the founders ( 8-10 years our seniors ) began hiring their college buddies as VP this, VP that.

It was around this time that the people I had worked with to build the entire system from scratch had started quitting. I should have taken the hint, but I stayed on.

When they hired a 'CTO' from their college who had dubious credentials at best, I should have known better than to stay. VPs with 0 management chops are still okay, but a CTO with no vision is a suicidal move. To make matters worse, I was put under direct management by him. He had no new ideas, and was quick to shoot down through intimidation any new work I tried working on as 'too optimistic'. Deep down, I knew that was not the problem - deep down he resented the fact that I was the go-to guy for the problems the newer employees faced, and try as he did, he couldn't solve problems to save his life. He resented having to come to me whenever something crashed, and there were instances of crashes he didn't even tell me about, and I only came to know of them through other employees who thought I should know.

I brought this into light at several meetings with the founders, the people who i had worked with since the beginning to build this system almost from scratch, and then rebuild it. However, the founders seemed more interested in reliving their college life than chiding the 'CTO' about his
misadventures.

This left a bad taste in my mouth, and I quit - but not before humiliating the 'CTO' at every public gathering with the team that we had, during my notice period - to the point that he stopped organizing these meetings. I was supported by the employees who knew who was to blame.

Soon after I left, two of these 'VP's were let go, and the 'CTO' had to make amends to accomodate several whims of the employees. They perhaps can't let the CTO go because he has had sexual harrassment charges against him, and wouldn't be hired anywhere else. This was probably the reason he went jobless for 2 years before the startup was founded.

I wish the startup succeeds, but I also wish he is not there to reap the benefits of the success he so doesn't deserve.

The point is - I could have just rolled over and taken it, and simply quit - but like I mentioned before - " The only thing needed for evil to succeed is for good people to do nothing about it."

So let it go, but not before you've done him enough harm so that he knows better than to mess with anyone else like he messed with you.