My friend's minecraft crashes everytime he joins the server.

Hi!
Me and my friends have a modded server. I will include the list of mods below.

Recently we added a few mods but no one had any trouble joining the game until yesterday. Everytime my friend tries to join our server his game crashes. I don't think it's a problem with mods - he can create singleplayer worlds normally and play on them. All versions of mods in his folder are the same as the rest of players.

I attached both the error message and our mod list in the "attachments"
Hopefully you will have better ideas of what to do than we do!

Ok so we have progress.

We deleted aether mod.

Our friend is a dumbass and decided to make an aether portal in nether SOMEHOW.

I think all we have to do now is to reset our nether