These look like some possibly interesting lines of interest from the log:
warn:module:load_dll Failed to load module L"aqProf.dll"; status=c0000135
warn:module:load_dll Failed to load module L"VtuneApi.dll"; status=c0000135
warn:module:load_dll Failed to load module L"VtuneApi32e.dll"; status=c0000135
warn:debugstr:OutputDebugStringA "LowLevelFatalError [File:F:\\Jenkins\\workspace\\MakeRomSteam\\Engine\\Source\\Runtime\\PakFile\\Private\\IPlatformFilePak.cpp] [Line: 3531] \nTrailing magic number (4197797455d) in '../../../MVCI/Content/Paks/pakchunk0-WindowsNoEditor_P.pak' is different than the expected one. Verify your installati"...
Verify your installati"...

Marvel Vs. Capcom Infinite launches and is technically playable using Proton 4.11-1. Unfortunately there is an issue with the frame rate being locked to 50fps for some reason. Since the game is intended to run at 60fps, this causes severe and constant stuttering, tearing and slowdowns, to the point of being extremely unpleasant to play. It also crashes frequently.

The game crashes when trying the online multiplayer mode with Proton 6.3-7 (I haven't tried with previous versions)
System Specs:
Proton logs:
steam-493840.tar.gz
Game still crashes when trying the online multiplayer with Proton 7:
Proton logs:
steam-493840-proton7.tar.gz
Specs:
Games still crashes with Proton 8.0-1 when trying the online multiplayer
Log file:
steam-493840.tar.gz
Specs
Reporting that I and another user are still experiencing the lobby crash issue that was listed to be resolved in Proton 9.0-2. We are experiencing an immediate crash when trying to join or create a lobby, however ranked and casual match via the in-game queue system still work as normal. The crash is occurring on the latest experimental as well as Proton version 9.0-4. The crash trigger immediately upon join or creation attempt and closes out the game and Steam entirely after hanging.
GPU: AMD Radeon 7
Driver/LLVM version: NVIDIA GeForce RTX 3080 - 4.6.0 NVIDIA 560.35.03
Kernel version: 6.9.3-76060903-generic
Link to full system information report as Gist
Proton version: Experimental (experimental-9.0-20241217) and Stable 9.0-4
Log Files: steam-493840.log
proton 9.0-2x1 2024-12proton 8.0-1x1 2023-04proton 6.3-7x1 2021-10proton 4.11-1x1 2019-08aqprof.dllx1 2019-05vtuneapi.dllx1 2019-05vtuneapi32e.dllx1 2019-05
Compatibility Report
System Information
I confirm:
steam-493840.log
Symptoms
Game crashes immediately after start.
Reproduction
Just launch the game.