1.15 is no longer supported on this forum, please update to 1.16 or 1.17 to receive support.

There's no crash here, does it crash to the launcher or does it just freeze?

I think -o must have been how you enabled or disabled online mode in ancient versions or something

Provide launcher_log.txt please

1.12 is no longer supported on this forum.

Please update to a modern version of Minecraft to receive support.

Can you provide a screenshot of your Minecrafty directory please

Are there any hs_err_pid files in your tmp directory?

Please provide debug.log

Please use one of the paste sites in my signature below to provide the log, Google Docs is going to try to add formatting that just gets in the way of reading logs

1.12 is no longer supported on this forum.

Please update to a modern version of Minecraft to receive support.

Forge changes nothing about a launcher, it just acts like a version of Minecraft

1.12 is no longer supported on this forum.

Please update to a modern version of Minecraft to receive support.

1.12 is no longer supported on this forum.

Please update to a modern version of Minecraft to receive support.

Strange... nothing useful
Do you have any files that start with hs_err_pid in your minecraft folder?

This shows a launcher run where you didn't try to launch the game.
I need you to provide the file after having tried to launch the game, without having restarted the launcher between the crash and providing the log

Provide /Users/erwan/Library/Application Support/minecraft/launcher_log.txt please

Looks like an issue with Quark's improved sleeping module, check for Quark updates and if there aren't any then report the issue

Try uninstalling Java completely before reinstalling, and I mean uninstall every version of Java

Does the installer run completely and say it was successful?
Is there no Forge version in the Minecraft Version dropdown afterwards?

If you answered yes to both of the above please list your antivirus programs

There should be an installer log next to the installer file if it even started to load correctly

You installed the server to your system directory, this is a MASSIVE no no

Remove MCMT

What did it say? Please provide screenshots

Try removing JustEnoughResources

I gave you a link to a youtube video in that message