The other mod is combat edit found here : https://www.curseforge.com/minecraft/mc-mods/combatedit
I use MultiMC with fabric.

I can launch and play the game with Carpet or Combat Edit with no issue. But if I try to launch with both mods active at the same time it fails with the message attached.
I have other mods but disabled them for this test, only fabric, carpet and combat edit where active.

latest.log

I was using both mods together with no issue on 1.17, the problem started when I tried using both in 1.18.1 with the corresponding mod updates.

It looks like a mixin conflict when using both mods, but tbh I don't know enough about mixins to pinpoint the exact problem.

I've got the same issue here :
[21:35:46] [main/ERROR]: Mixin apply for mod combatedit failed combatedit.mixins.json:PlayerEntityMixin -> net.minecraft.class_1657: org.spongepowered.asm.mixin.injection.throwables.InvalidInjectionException Variable modifier target for net/minecraft/class_1657::checkIfSweepEnchant was removed by another injector [INJECT Applicator Phase -> combatedit.mixins.json:PlayerEntityMixin -> Apply Injections -> -> Inject -> combatedit.mixins.json:PlayerEntityMixin->@ModifyVariable::checkIfSweepEnchant(Z)Z from mod combatedit]
org.spongepowered.asm.mixin.injection.throwables.InvalidInjectionException: Variable modifier target for net/minecraft/class_1657::checkIfSweepEnchant was removed by another injector [INJECT Applicator Phase -> combatedit.mixins.json:PlayerEntityMixin -> Apply Injections -> -> Inject -> combatedit.mixins.json:PlayerEntityMixin->@ModifyVariable::checkIfSweepEnchant(Z)Z from mod combatedit]
at org.spongepowered.asm.mixin.injection.modify.ModifyVariableInjector.inject(ModifyVariableInjector.java:169) ~[sponge-mixin-0.10.7+mixin.0.8.4.jar:0.10.7+mixin.0.8.4]
at org.spongepowered.asm.mixin.injection.code.Injector.inject(Injector.java:276) ~[sponge-mixin-0.10.7+mixin.0.8.4.jar:0.10.7+mixin.0.8.4]
at org.spongepowered.asm.mixin.injection.struct.InjectionInfo.inject(InjectionInfo.java:445) ~[sponge-mixin-0.10.7+mixin.0.8.4.jar:0.10.7+mixin.0.8.4]
at org.spongepowered.asm.mixin.transformer.MixinTargetContext.applyInjections(MixinTargetContext.java:1374) ~[sponge-mixin-0.10.7+mixin.0.8.4.jar:0.10.7+mixin.0.8.4]
at org.spongepowered.asm.mixin.transformer.MixinApplicatorStandard.applyInjections(MixinApplicatorStandard.java:1052) ~[sponge-mixin-0.10.7+mixin.0.8.4.jar:0.10.7+mixin.0.8.4]
at org.spongepowered.asm.mixin.transformer.MixinApplicatorStandard.applyMixin(MixinApplicatorStandard.java:400) ~[sponge-mixin-0.10.7+mixin.0.8.4.jar:0.10.7+mixin.0.8.4]
at org.spongepowered.asm.mixin.transformer.MixinApplicatorStandard.apply(MixinApplicatorStandard.java:325) ~[sponge-mixin-0.10.7+mixin.0.8.4.jar:0.10.7+mixin.0.8.4]
at org.spongepowered.asm.mixin.transformer.TargetClassContext.apply(TargetClassContext.java:421) ~[sponge-mixin-0.10.7+mixin.0.8.4.jar:0.10.7+mixin.0.8.4]
at org.spongepowered.asm.mixin.transformer.TargetClassContext.applyMixins(TargetClassContext.java:403) ~[sponge-mixin-0.10.7+mixin.0.8.4.jar:0.10.7+mixin.0.8.4]
at org.spongepowered.asm.mixin.transformer.MixinProcessor.applyMixins(MixinProcessor.java:363) [sponge-mixin-0.10.7+mixin.0.8.4.jar:0.10.7+mixin.0.8.4]
at org.spongepowered.asm.mixin.transformer.MixinTransformer.transformClass(MixinTransformer.java:234) [sponge-mixin-0.10.7+mixin.0.8.4.jar:0.10.7+mixin.0.8.4]
at org.spongepowered.asm.mixin.transformer.MixinTransformer.transformClassBytes(MixinTransformer.java:202) [sponge-mixin-0.10.7+mixin.0.8.4.jar:0.10.7+mixin.0.8.4]
at net.fabricmc.loader.impl.launch.knot.KnotClassDelegate.getPostMixinClassByteArray(KnotClassDelegate.java:247) [fabric-loader-0.12.12.jar:?]
at net.fabricmc.loader.impl.launch.knot.KnotClassDelegate.tryLoadClass(KnotClassDelegate.java:150) [fabric-loader-0.12.12.jar:?]
at net.fabricmc.loader.impl.launch.knot.KnotClassLoader.loadClass(KnotClassLoader.java:155) [fabric-loader-0.12.12.jar:?]
at java.lang.ClassLoader.loadClass(ClassLoader.java:520) [?:?]
at net.minecraft.class_6396.handler$zil000$fillSystemDetails(class_6396.java:522) [server-intermediary.jar:?]
at net.minecraft.class_6396.(class_6396.java:57) [server-intermediary.jar:?]
at net.minecraft.class_128.(class_128.java:32) [server-intermediary.jar:?]
at net.minecraft.class_128.method_24305(class_128.java:272) [server-intermediary.jar:?]
at net.minecraft.server.Main.main(Main.java:94) [server-intermediary.jar:?]
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:?]
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77) ~[?:?]
at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:?]
at java.lang.reflect.Method.invoke(Method.java:568) ~[?:?]
at net.fabricmc.loader.impl.game.minecraft.MinecraftGameProvider.launch(MinecraftGameProvider.java:608) [fabric-loader-0.12.12.jar:?]
at net.fabricmc.loader.impl.launch.knot.Knot.launch(Knot.java:77) [fabric-loader-0.12.12.jar:?]
at net.fabricmc.loader.impl.launch.knot.KnotServer.main(KnotServer.java:23) [fabric-loader-0.12.12.jar:?]
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:?]
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77) ~[?:?]
at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:?]
at java.lang.reflect.Method.invoke(Method.java:568) ~[?:?]
at net.fabricmc.loader.impl.launch.server.FabricServerLauncher.main(FabricServerLauncher.java:66) [fabric-loader-0.12.12.jar:?]
[21:35:46] [main/FATAL]: Failed to start the minecraft server
java.lang.RuntimeException: Mixin transformation of net.minecraft.class_1657 failed
at net.fabricmc.loader.impl.launch.knot.KnotClassDelegate.getPostMixinClassByteArray(KnotClassDelegate.java:252) ~[fabric-loader-0.12.12.jar:?]
at net.fabricmc.loader.impl.launch.knot.KnotClassDelegate.tryLoadClass(KnotClassDelegate.java:150) ~[fabric-loader-0.12.12.jar:?]
at net.fabricmc.loader.impl.launch.knot.KnotClassLoader.loadClass(KnotClassLoader.java:155) ~[fabric-loader-0.12.12.jar:?]
at java.lang.ClassLoader.loadClass(ClassLoader.java:520) ~[?:?]
at net.minecraft.class_6396.handler$zil000$fillSystemDetails(class_6396.java:522) ~[server-intermediary.jar:?]
at net.minecraft.class_6396.(class_6396.java:57) ~[server-intermediary.jar:?]
at net.minecraft.class_128.(class_128.java:32) ~[server-intermediary.jar:?]
at net.minecraft.class_128.method_24305(class_128.java:272) ~[server-intermediary.jar:?]
at net.minecraft.server.Main.main(Main.java:94) [server-intermediary.jar:?]
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:?]
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77) ~[?:?]
at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:?]
at java.lang.reflect.Method.invoke(Method.java:568) ~[?:?]
at net.fabricmc.loader.impl.game.minecraft.MinecraftGameProvider.launch(MinecraftGameProvider.java:608) [fabric-loader-0.12.12.jar:?]
at net.fabricmc.loader.impl.launch.knot.Knot.launch(Knot.java:77) [fabric-loader-0.12.12.jar:?]
at net.fabricmc.loader.impl.launch.knot.KnotServer.main(KnotServer.java:23) [fabric-loader-0.12.12.jar:?]
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:?]
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77) ~[?:?]
at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:?]
at java.lang.reflect.Method.invoke(Method.java:568) ~[?:?]
at net.fabricmc.loader.impl.launch.server.FabricServerLauncher.main(FabricServerLauncher.java:66) [fabric-loader-0.12.12.jar:?]
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) ~[sponge-mixin-0.10.7+mixin.0.8.4.jar:0.10.7+mixin.0.8.4]
at org.spongepowered.asm.mixin.transformer.MixinTransformer.transformClass(MixinTransformer.java:234) ~[sponge-mixin-0.10.7+mixin.0.8.4.jar:0.10.7+mixin.0.8.4]
at org.spongepowered.asm.mixin.transformer.MixinTransformer.transformClassBytes(MixinTransformer.java:202) ~[sponge-mixin-0.10.7+mixin.0.8.4.jar:0.10.7+mixin.0.8.4]
at net.fabricmc.loader.impl.launch.knot.KnotClassDelegate.getPostMixinClassByteArray(KnotClassDelegate.java:247) ~[fabric-loader-0.12.12.jar:?]
... 20 more
Caused by: org.spongepowered.asm.mixin.throwables.MixinApplyError: Mixin [combatedit.mixins.json:PlayerEntityMixin] from phase [DEFAULT] in config [combatedit.mixins.json] from mod [combatedit] FAILED during APPLY
at org.spongepowered.asm.mixin.transformer.MixinProcessor.handleMixinError(MixinProcessor.java:638) ~[sponge-mixin-0.10.7+mixin.0.8.4.jar:0.10.7+mixin.0.8.4]
at org.spongepowered.asm.mixin.transformer.MixinProcessor.handleMixinApplyError(MixinProcessor.java:589) ~[sponge-mixin-0.10.7+mixin.0.8.4.jar:0.10.7+mixin.0.8.4]
at org.spongepowered.asm.mixin.transformer.MixinProcessor.applyMixins(MixinProcessor.java:379) ~[sponge-mixin-0.10.7+mixin.0.8.4.jar:0.10.7+mixin.0.8.4]
at org.spongepowered.asm.mixin.transformer.MixinTransformer.transformClass(MixinTransformer.java:234) ~[sponge-mixin-0.10.7+mixin.0.8.4.jar:0.10.7+mixin.0.8.4]
at org.spongepowered.asm.mixin.transformer.MixinTransformer.transformClassBytes(MixinTransformer.java:202) ~[sponge-mixin-0.10.7+mixin.0.8.4.jar:0.10.7+mixin.0.8.4]
at net.fabricmc.loader.impl.launch.knot.KnotClassDelegate.getPostMixinClassByteArray(KnotClassDelegate.java:247) ~[fabric-loader-0.12.12.jar:?]
... 20 more
Caused by: org.spongepowered.asm.mixin.injection.throwables.InvalidInjectionException: Variable modifier target for net/minecraft/class_1657::checkIfSweepEnchant was removed by another injector [INJECT Applicator Phase -> combatedit.mixins.json:PlayerEntityMixin -> Apply Injections -> -> Inject -> combatedit.mixins.json:PlayerEntityMixin->@ModifyVariable::checkIfSweepEnchant(Z)Z from mod combatedit]
at org.spongepowered.asm.mixin.injection.modify.ModifyVariableInjector.inject(ModifyVariableInjector.java:169) ~[sponge-mixin-0.10.7+mixin.0.8.4.jar:0.10.7+mixin.0.8.4]
at org.spongepowered.asm.mixin.injection.code.Injector.inject(Injector.java:276) ~[sponge-mixin-0.10.7+mixin.0.8.4.jar:0.10.7+mixin.0.8.4]
at org.spongepowered.asm.mixin.injection.struct.InjectionInfo.inject(InjectionInfo.java:445) ~[sponge-mixin-0.10.7+mixin.0.8.4.jar:0.10.7+mixin.0.8.4]
at org.spongepowered.asm.mixin.transformer.MixinTargetContext.applyInjections(MixinTargetContext.java:1374) ~[sponge-mixin-0.10.7+mixin.0.8.4.jar:0.10.7+mixin.0.8.4]
at org.spongepowered.asm.mixin.transformer.MixinApplicatorStandard.applyInjections(MixinApplicatorStandard.java:1052) ~[sponge-mixin-0.10.7+mixin.0.8.4.jar:0.10.7+mixin.0.8.4]
at org.spongepowered.asm.mixin.transformer.MixinApplicatorStandard.applyMixin(MixinApplicatorStandard.java:400) ~[sponge-mixin-0.10.7+mixin.0.8.4.jar:0.10.7+mixin.0.8.4]
at org.spongepowered.asm.mixin.transformer.MixinApplicatorStandard.apply(MixinApplicatorStandard.java:325) ~[sponge-mixin-0.10.7+mixin.0.8.4.jar:0.10.7+mixin.0.8.4]
at org.spongepowered.asm.mixin.transformer.TargetClassContext.apply(TargetClassContext.java:421) ~[sponge-mixin-0.10.7+mixin.0.8.4.jar:0.10.7+mixin.0.8.4]
at org.spongepowered.asm.mixin.transformer.TargetClassContext.applyMixins(TargetClassContext.java:403) ~[sponge-mixin-0.10.7+mixin.0.8.4.jar:0.10.7+mixin.0.8.4]
at org.spongepowered.asm.mixin.transformer.MixinProcessor.applyMixins(MixinProcessor.java:363) ~[sponge-mixin-0.10.7+mixin.0.8.4.jar:0.10.7+mixin.0.8.4]
at org.spongepowered.asm.mixin.transformer.MixinTransformer.transformClass(MixinTransformer.java:234) ~[sponge-mixin-0.10.7+mixin.0.8.4.jar:0.10.7+mixin.0.8.4]
at org.spongepowered.asm.mixin.transformer.MixinTransformer.transformClassBytes(MixinTransformer.java:202) ~[sponge-mixin-0.10.7+mixin.0.8.4.jar:0.10.7+mixin.0.8.4]
at net.fabricmc.loader.impl.launch.knot.KnotClassDelegate.getPostMixinClassByteArray(KnotClassDelegate.java:247) ~[fabric-loader-0.12.12.jar:?]
... 20 more