Quick Answer
On RTX 4090, Lethal Company anti-cheat errors are usually caused by mod loader mismatches, damaged Steam files, overlays, or outdated drivers, not by the hardware itself. The safe fix is to remove mod loaders first, verify the game files, restart Steam, and test a clean vanilla launch before changing drivers. Do not use patched executables or bypass tools; they create more risk than they solve.
Start with a clean launch
Launch the game without BepInEx, Thunderstore profiles, custom DLLs, launch arguments, or overlays. If the clean game opens, the fault is almost certainly a mod version or profile issue. If it still fails, verify files, reboot, and check that Windows, Steam, and the GPU driver are current.
Device-specific checks
RTX 4090 has more than enough power for Lethal Company when the software stack is healthy; even modest systems should target around 100 fps at 1080p on a suitable CPU. Handhelds should be tested on their standard performance mode before tuning, while desktop RTX cards should use a recent NVIDIA driver and default control-panel settings. Keep antivirus exclusions cautious and only for trusted game folders.
Mods and multiplayer safety
Lethal Company groups often fail when one player has a different mod version, extra dependency, or outdated profile. Rebuild the mod pack from a known shared list and test with one host before a full lobby. If the issue appears only online, check lobby mods, invite flow, and Steam connectivity before blaming the GPU.
FAQ
Is this problem caused by RTX 4090?
Usually no. RTX 4090 is capable of running Lethal Company; the more common cause is a mod, file, driver, or overlay conflict.
Should I delete all mods?
For testing, yes. Move the mod profile aside, launch the vanilla game, then add the shared mod pack back in small groups until the failure returns.
What if the game still fails after file verification?
Update the GPU driver, disable overlays, reboot, and test a new save or lobby. If only one profile fails, keep the clean profile and rebuild the old one carefully.
