DaemonUmbra

Please provide the debug.log as described in my signature and the EAQ

Please provide a screenshot of your .minecraft folder

NBT is the format in which the data is written to disk. https://minecraft.gamepedia.com/NBT_format

1.6.4 is no longer supported on this forum due to its age. Please update to a modern version of Minecraft to receive support.

You shouldn't need a tutorial for it, Installation Tab -> New -> Select Minecraft Version, Game Directory (where you want mods, logs, and a configs to be generated), and Java version -> Save -> Play

Be more specific please what didn't work about making a new Profile/Installation?

This is starting to go from "Support and Bug Reports" to "Mods" if you want to make a thread that advertises your mod please do so in the correct subforum instead of your support thread.

Enough of them that you should know that's not true.

What launcher are you using? Please provide a screenshot.

Why are you running such an ancient version of Forge?

The filenames of one or more of your mods suggests you got them from a repost site. Please read up on the StopModReposts project (link in my signature) for info on why this is a bad thing.

Forge installs itself as a version of Minecraft. Make a new Profile/Installation and select Forge from the version dropdown. (Note: For some reason Forge 1.12.2 gets booted to the bottom of the list.)

Please provide logs for 1.14.4 as 1.8.9 is not supported on this forum anymore.

you put Programm Files instead of Program Files

Try the most recent version of Forge for 1.12.2

What mods did you add?

Is this a pre-made modpack or something you made?

Yes that screen is saying that you have duplicate mods... provide the debug.log from a crash with just one copy of NetherEx in

Give a URL, many sites pretend to be the official website to get you to click on their links, often providing mislabeled and outdated versions such as the one you have.

The dev was using over-shortened mod IDs and changed them, netherex used to be nex and libraryex apparently used to be lex. Try the most recent versions of both.

Where are you getting Forge?

Old thread, you do not have the same error, and you are using Fabric instead of Forge.

What do you need the library for? What library is it?

What version of NetherEx do you have?