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When I try to launch Forge it downloads the required files, closed, then reloads and brings up this error in the Game Output tab of the launcher:

[21:55:03] [main/INFO] [LaunchWrapper]: Loading tweak class name net.minecraftforge.fml.common.launcher.FMLTweaker
[21:55:03] [main/INFO] [LaunchWrapper]: Using primary tweak class name net.minecraftforge.fml.common.launcher.FMLTweaker
[21:55:03] [main/INFO] [LaunchWrapper]: Calling tweak class net.minecraftforge.fml.common.launcher.FMLTweaker
[21:55:03] [main/INFO] [FML]: Forge Mod Loader version 8.0.73.1361 for Minecraft 1.8 loading
[21:55:03] [main/INFO] [FML]: Java is Java HotSpot(TM) 64-Bit Server VM, version 1.8.0_25, running on Windows 8.1:amd64:6.3, installed at C:\Program Files (x86)\Minecraft\runtime\jre-x64\1.8.0_25
[21:55:03] [main/WARN] [FML]: The coremod invtweaks.forge.asm.FMLPlugin does not have a MCVersion annotation, it may cause issues with this version of Minecraft
[21:55:03] [main/WARN] [FML]: The coremod codechicken.nei.asm.NEICorePlugin does not have a MCVersion annotation, it may cause issues with this version of Minecraft
[21:55:03] [main/INFO] [LaunchWrapper]: Loading tweak class name net.minecraftforge.fml.common.launcher.FMLInjectionAndSortingTweaker
[21:55:03] [main/INFO] [LaunchWrapper]: Loading tweak class name net.minecraftforge.fml.common.launcher.FMLDeobfTweaker
[21:55:03] [main/INFO] [LaunchWrapper]: Calling tweak class net.minecraftforge.fml.common.launcher.FMLInjectionAndSortingTweaker
[21:55:03] [main/INFO] [LaunchWrapper]: Calling tweak class net.minecraftforge.fml.common.launcher.FMLInjectionAndSortingTweaker
[21:55:03] [main/INFO] [LaunchWrapper]: Calling tweak class net.minecraftforge.fml.relauncher.CoreModManager$FMLPluginWrapper
[21:55:06] [main/INFO] [FML]: Found valid fingerprint for Minecraft Forge. Certificate fingerprint e3c3d50c7c986df74c645c0ac54639741c90a557
[21:55:06] [main/INFO] [FML]: Found valid fingerprint for Minecraft. Certificate fingerprint cd99959656f753dc28d863b46769f7f8fbaefcfc
[21:55:07] [main/INFO] [LaunchWrapper]: Calling tweak class net.minecraftforge.fml.relauncher.CoreModManager$FMLPluginWrapper
[21:55:07] [main/INFO] [LaunchWrapper]: Calling tweak class net.minecraftforge.fml.relauncher.CoreModManager$FMLPluginWrapper
[21:55:07] [main/INFO] [LaunchWrapper]: Calling tweak class net.minecraftforge.fml.relauncher.CoreModManager$FMLPluginWrapper
Exception in thread "main" [21:55:07] [main/INFO] [STDERR]: [java.lang.Throwable$WrappedPrintStream:println:748]: java.lang.NoClassDefFoundError: codechicken/core/launch/CodeChickenCorePlugin
[21:55:07] [main/INFO] [STDERR]: [java.lang.Throwable$WrappedPrintStream:println:748]: at codechicken.nei.asm.NEICorePlugin.getASMTransformerClass(NEICorePlugin.java:18)
[21:55:07] [main/INFO] [STDERR]: [java.lang.Throwable$WrappedPrintStream:println:748]: at net.minecraftforge.fml.relauncher.CoreModManager$FMLPluginWrapper.injectIntoClassLoader(CoreModManager.java:115)
[21:55:07] [main/INFO] [STDERR]: [java.lang.Throwable$WrappedPrintStream:println:748]: at net.minecraft.launchwrapper.Launch.launch(Launch.java:115)
[21:55:07] [main/INFO] [STDERR]: [java.lang.Throwable$WrappedPrintStream:println:748]: at net.minecraft.launchwrapper.Launch.main(Launch.java:28)
[21:55:07] [main/INFO] [STDERR]: [java.lang.Throwable$WrappedPrintStream:println:748]: Caused by: java.lang.ClassNotFoundException: codechicken.core.launch.CodeChickenCorePlugin
[21:55:07] [main/INFO] [STDERR]: [java.lang.Throwable$WrappedPrintStream:println:748]: at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:191)
[21:55:07] [main/INFO] [STDERR]: [java.lang.Throwable$WrappedPrintStream:println:748]: at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
[21:55:07] [main/INFO] [STDERR]: [java.lang.Throwable$WrappedPrintStream:println:748]: at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
[21:55:07] [main/INFO] [STDERR]: [java.lang.Throwable$WrappedPrintStream:println:748]: ... 4 more
[21:55:07] [main/INFO] [STDERR]: [java.lang.Throwable$WrappedPrintStream:println:748]: Caused by: java.lang.NullPointerException
[21:55:07] [main/INFO] [STDERR]: [java.lang.Throwable$WrappedPrintStream:println:748]: at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:182)
[21:55:07] [main/INFO] [STDERR]: [java.lang.Throwable$WrappedPrintStream:println:748]: ... 6 more

If some of your mods are not compatible with the version of Forge that you are using (Ex. TooManyItems1.6.4 running on Forge 1.7.10) then get those outdated mods out of your mods folder. Even if you have just ONE outdated mod, it will cause Forge to crash. If this isn't the reason then I'm not too sure why your Forge is crashing, try reinstalling it, or googling/youtube searching.

I had the CodeChickenCore, as well as NotEnoughItems to work installed, but I uninstalled and not Forge will not launch at all.

Seems to be working fine now I'm not sure what I did to make it work, but whatever it was worked.