I don't know anything about programming nor do I understand the slightest thing that it says here, this threw me the Fabric loader and I just copy and paste it:
(note: this happened to me right after installing OptiFabric and Optifine, I had been playing with many mods since before without any problem and using Sodium & Iris)

Minecraft has crashed!
net.fabricmc.loader.impl.FormattedException: java.lang.ExceptionInInitializerError
at net.fabricmc.loader.impl.FormattedException.ofLocalized(FormattedException.java:63)
at net.fabricmc.loader.impl.game.minecraft.MinecraftGameProvider.launch(MinecraftGameProvider.java:470)
at net.fabricmc.loader.impl.launch.knot.Knot.launch(Knot.java:74)
at net.fabricmc.loader.impl.launch.knot.KnotClient.main(KnotClient.java:23)
Caused by: java.lang.ExceptionInInitializerError
at net.minecraft.class_128.method_568(class_128.java:175)
at net.minecraft.class_128.method_24305(class_128.java:345)
at net.minecraft.client.main.Main.main(Main.java:164)
at net.fabricmc.loader.impl.game.minecraft.MinecraftGameProvider.launch(MinecraftGameProvider.java:468)
... 2 more
Caused by: java.lang.RuntimeException: Mixin transformation of net.minecraft.class_425 failed
at net.fabricmc.loader.impl.launch.knot.KnotClassDelegate.getPostMixinClassByteArray(KnotClassDelegate.java:427)
at net.fabricmc.loader.impl.launch.knot.KnotClassDelegate.tryLoadClass(KnotClassDelegate.java:323)
at net.fabricmc.loader.impl.launch.knot.KnotClassDelegate.loadClass(KnotClassDelegate.java:218)
at net.fabricmc.loader.impl.launch.knot.KnotClassLoader.loadClass(KnotClassLoader.java:112)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:520)
at java.base/java.lang.Class.getDeclaredFields0(Native Method)
at java.base/java.lang.Class.privateGetDeclaredFields(Class.java:3297)
at java.base/java.lang.Class.getDeclaredFields(Class.java:2371)
at net.optifine.reflect.FieldLocatorTypes.(FieldLocatorTypes.java:25)
at net.optifine.reflect.Reflector.(Reflector.java:541)
... 6 more
Caused by: org.spongepowered.asm.mixin.transformer.throwables.MixinTransformerError: An unexpected critical error was encountered
at org.spongepowered.asm.mixin.transformer.MixinProcessor.applyMixins(MixinProcessor.java:392)
at org.spongepowered.asm.mixin.transformer.MixinTransformer.transformClass(MixinTransformer.java:234)
at org.spongepowered.asm.mixin.transformer.MixinTransformer.transformClassBytes(MixinTransformer.java:202)
at net.fabricmc.loader.impl.launch.knot.KnotClassDelegate.getPostMixinClassByteArray(KnotClassDelegate.java:422)
... 15 more
Caused by: org.spongepowered.asm.mixin.throwables.MixinApplyError: Mixin [dark-loading-screen.mixins.json:compat.optifine.SplashOverlayMixin from mod dark-loading-screen] from phase [DEFAULT] in config [dark-loading-screen.mixins.json] FAILED during APPLY
at org.spongepowered.asm.mixin.transformer.MixinProcessor.handleMixinError(MixinProcessor.java:638)
at org.spongepowered.asm.mixin.transformer.MixinProcessor.handleMixinApplyError(MixinProcessor.java:589)
at org.spongepowered.asm.mixin.transformer.MixinProcessor.applyMixins(MixinProcessor.java:379)
... 18 more
Caused by: org.spongepowered.asm.mixin.injection.throwables.InvalidInjectionException: Specified index 5 for @ModifyArg is invalid for args (IIIII), expected I on net/minecraft/class_425::adjustBarColor [INJECT Applicator Phase -> dark-loading-screen.mixins.json:compat.optifine.SplashOverlayMixin from mod dark-loading-screen -> Apply Injections -> -> Inject -> dark-loading-screen.mixins.json:compat.optifine.SplashOverlayMixin from mod dark-loading-screen->@ModifyArg::adjustBarColor(I)I]
at org.spongepowered.asm.mixin.injection.invoke.ModifyArgInjector.findArgIndex(ModifyArgInjector.java:158)
at org.spongepowered.asm.mixin.injection.invoke.ModifyArgInjector.injectAtInvoke(ModifyArgInjector.java:113)
at org.spongepowered.asm.mixin.injection.invoke.InvokeInjector.inject(InvokeInjector.java:82)
at org.spongepowered.asm.mixin.injection.invoke.ModifyArgInjector.inject(ModifyArgInjector.java:103)
at org.spongepowered.asm.mixin.injection.code.Injector.inject(Injector.java:276)
at org.spongepowered.asm.mixin.injection.struct.InjectionInfo.inject(InjectionInfo.java:445)
at org.spongepowered.asm.mixin.transformer.MixinTargetContext.applyInjections(MixinTargetContext.java:1377)
at org.spongepowered.asm.mixin.transformer.MixinApplicatorStandard.applyInjections(MixinApplicatorStandard.java:1062)
at org.spongepowered.asm.mixin.transformer.MixinApplicatorStandard.applyMixin(MixinApplicatorStandard.java:402)
at org.spongepowered.asm.mixin.transformer.MixinApplicatorStandard.apply(MixinApplicatorStandard.java:327)
at org.spongepowered.asm.mixin.transformer.TargetClassContext.apply(TargetClassContext.java:421)
at org.spongepowered.asm.mixin.transformer.TargetClassContext.applyMixins(TargetClassContext.java:403)
at org.spongepowered.asm.mixin.transformer.MixinProcessor.applyMixins(MixinProcessor.java:363)
... 18 more

The crash is caused by dark-loading-screen. They have a mixin that should add Optifabric compatibility but it seems like it isn't working properly. Please post the issue on that repository and next time provide a list of mods as figuring stuff out from a stack trace is hard, especially when you title the issue "crash :/"