As soon as I open forge with the mods installed it just crashes.

---- Minecraft Crash Report ----

WARNING: coremods are present:
Contact their authors BEFORE contacting forge

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Time: 8/26/19 4:45 PM
Description: Initializing game

java.lang.NoClassDefFoundError: net/minecraft/client/renderer/EntityRenderer
at net.minecraftforge.client.ForgeHooksClient.shouldUseVanillaReloadableListener(ForgeHooksClient.java:959)
at net.minecraft.client.resources.SimpleReloadableResourceManager.func_110544_b(SimpleReloadableResourceManager.java:131)
at net.minecraft.client.resources.SimpleReloadableResourceManager.func_110541_a(SimpleReloadableResourceManager.java:112)
at net.minecraft.client.Minecraft.func_110436_a(Minecraft.java:808)
at net.minecraftforge.fml.client.FMLClientHandler.beginMinecraftLoading(FMLClientHandler.java:247)
at net.minecraft.client.Minecraft.func_71384_a(Minecraft.java:467)
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:378)
at net.minecraft.client.main.Main.main(SourceFile:123)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at net.minecraft.launchwrapper.Launch.launch(Launch.java:135)
at net.minecraft.launchwrapper.Launch.main(Launch.java:28)
Caused by: java.lang.ClassNotFoundException: net.minecraft.client.renderer.EntityRenderer
at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:191)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
... 14 more
Caused by: org.spongepowered.asm.mixin.transformer.throwables.MixinTransformerError: An unexpected critical error was encountered
at org.spongepowered.asm.mixin.transformer.MixinTransformer.transformClassBytes(MixinTransformer.java:521)
at org.spongepowered.asm.mixin.transformer.Proxy.transform(Proxy.java:72)
at net.minecraft.launchwrapper.LaunchClassLoader.runTransformers(LaunchClassLoader.java:279)
at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:176)
... 16 more
Caused by: java.lang.RuntimeException: java.lang.ClassNotFoundException: kotlin.Pair
at org.spongepowered.asm.mixin.transformer.MixinPreProcessorStandard.transformMethod(MixinPreProcessorStandard.java:682)
at org.spongepowered.asm.mixin.transformer.MixinPreProcessorStandard.transform(MixinPreProcessorStandard.java:670)
at org.spongepowered.asm.mixin.transformer.MixinPreProcessorStandard.attach(MixinPreProcessorStandard.java:267)
at org.spongepowered.asm.mixin.transformer.MixinPreProcessorStandard.createContextFor(MixinPreProcessorStandard.java:241)
at org.spongepowered.asm.mixin.transformer.MixinInfo.createContextFor(MixinInfo.java:1144)
at org.spongepowered.asm.mixin.transformer.MixinApplicatorStandard.apply(MixinApplicatorStandard.java:267)
at org.spongepowered.asm.mixin.transformer.TargetClassContext.applyMixins(TargetClassContext.java:353)
at org.spongepowered.asm.mixin.transformer.MixinTransformer.apply(MixinTransformer.java:724)
at org.spongepowered.asm.mixin.transformer.MixinTransformer.applyMixins(MixinTransformer.java:703)
at org.spongepowered.asm.mixin.transformer.MixinTransformer.transformClassBytes(MixinTransformer.java:509)
... 19 more
Caused by: java.lang.ClassNotFoundException: kotlin.Pair
... 29 more

A detailed walkthrough of the error, its code path and all known details is as follows:

-- Head --
Thread: Client thread
Stacktrace:
at net.minecraftforge.client.ForgeHooksClient.shouldUseVanillaReloadableListener(ForgeHooksClient.java:959)
at net.minecraft.client.resources.SimpleReloadableResourceManager.func_110544_b(SimpleReloadableResourceManager.java:131)
at net.minecraft.client.resources.SimpleReloadableResourceManager.func_110541_a(SimpleReloadableResourceManager.java:112)
at net.minecraft.client.Minecraft.func_110436_a(Minecraft.java:808)
at net.minecraftforge.fml.client.FMLClientHandler.beginMinecraftLoading(FMLClientHandler.java:247)
at net.minecraft.client.Minecraft.func_71384_a(Minecraft.java:467)

-- Initialization --
Details:
Stacktrace:
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:378)
at net.minecraft.client.main.Main.main(SourceFile:123)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at net.minecraft.launchwrapper.Launch.launch(Launch.java:135)
at net.minecraft.launchwrapper.Launch.main(Launch.java:28)

-- System Details --
Details:
Minecraft Version: 1.12.2
Operating System: Windows 10 (amd64) version 10.0
Java Version: 1.8.0_51, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 325495904 bytes (310 MB) / 805306368 bytes (768 MB) up to 2147483648 bytes (2048 MB)
JVM Flags: 8 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx2G -XX:+UnlockExperimentalVMOptions -XX:+UseG1GC -XX:G1NewSizePercent=20 -XX:G1ReservePercent=20 -XX:MaxGCPauseMillis=50 -XX:G1HeapRegionSize=32M
IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
FML: MCP 9.42 Powered by Forge 14.23.5.2838 5 mods loaded, 5 mods active
States: 'U' = Unloaded 'L' = Loaded 'C' = Constructed 'H' = Pre-initialized 'I' = Initialized 'J' = Post-initialized 'A' = Available 'D' = Disabled 'E' = Errored

| State | ID            | Version      | Source                        | Signature                                |
|:----- |:------------- |:------------ |:----------------------------- |:---------------------------------------- |
| L     | minecraft     | 1.12.2       | minecraft.jar                 | None                                     |
| L     | mcp           | 9.42         | minecraft.jar                 | None                                     |
| L     | FML           | 8.0.99.99    | forge-1.12.2-14.23.5.2838.jar | e3c3d50c7c986df74c645c0ac54639741c90a557 |
| L     | forge         | 14.23.5.2838 | forge-1.12.2-14.23.5.2838.jar | e3c3d50c7c986df74c645c0ac54639741c90a557 |
| L     | betterportals | 0.2.6        | betterportals-0.2.6.jar       | None                                     |

Loaded coremods (and transformers): 
GL info: ' Vendor: 'Intel' Version: '4.5.0 - Build 23.20.16.4905' Renderer: 'Intel(R) UHD Graphics 620'
Launched Version: 1.12.2-forge1.12.2-14.23.5.2838
LWJGL: 2.9.4
OpenGL: Intel(R) UHD Graphics 620 GL version 4.5.0 - Build 23.20.16.4905, Intel
GL Caps: Using GL 1.3 multitexturing.

Using GL 1.3 texture combiners.
Using framebuffer objects because OpenGL 3.0 is supported and separate blending is supported.
Shaders are available because OpenGL 2.1 is supported.
VBOs are available because OpenGL 1.5 is supported.

Using VBOs: Yes
Is Modded: Definitely; Client brand changed to 'fml,forge'
Type: Client (map_client.txt)
Resource Packs: 
Current Language: ~~ERROR~~ NullPointerException: null
Profiler Position: N/A (disabled)
CPU: 8x Intel(R) Core(TM) i7-8550U CPU @ 1.80GHz

i tried downloading the reccommended version of forge 1.12.2 and it still didnt work

im also using the 0.2.6 version of better portals

You don't have forgelin installed. BP depends on it. Install it first and it'll launch.

all good, thanks