Today I completely forgot how to login to a LXC container running in the Proxmox environment.

To reset the root password for a specific VM, you first need to find the VM ID in the proxmox control panel. In my case, it was 108

Then, perform the following commands in the proxmox host as root:

lxc-attach -n <vmid>
passwd <password>
exit

Replacing with 108 and with your desired password