FCPX crashing immediately.

Have you done any updates to your computer or FCPX about the time this started?

What version MacOS and FCPX are you running?

Are you reinstalling from the App Store?

As Tom sugguested, try creating a new user and boot into that user and check to see if it's still crashing.

Have you tried booting in Safe Mode? Restart your mac holding down the SHIFT key. See if that makes a difference to the crash.

The problem is a conflict in the main user. As Luis said generate an EtreCheck report using full drive access from the application preferences. To produce a report use File->New Report. Then use the copy report function and paste it using the Additional Text button in the reply box.. The application is a free download from the App Store. 

A couple of things stand out. One is the drives look Full. The system drive seems to have less than the absolutely minimum 15% free space. The Other thing is that CleanMyMac has been installed. It looks like you did this after the problem occurred. Unfortunately that probably damaged the system further.

What Luis said.

Yes, but in a very specific way - see below.

By a clean install we mean completely erasing the drive and then installing. I have written down a full list of instructions for that, and will post later today since I am not at my mac now.

After doing the clean install and when asked you can elect to import from another mac, or from a Time Machine backup. Then you must choose ONLY the user accounts. Do NOT check applications, settings or other files, or you’d be negating the effects of the clean install.

Try it in a new admin user as a test.

In addition to what Tom said, please run Etrecheck and post its full report here. The information from that report may help us find the cause of the problem.

This machine has remnants of the hideous “cleanmymac”...

You need to have a full backup and do a clean install.

Probably worse.

The clean install migrating the user should Not lose anything.