So Arch GNU/Linux isn't booting after a kernel update? No issue.
Write the current Arch GNU/Linux ISO image to a USB drive you have lying around:
sudo dd if=archlinux-2016.10.01-dual.iso of=/dev/sdX
Boot from the USB into a live session of the same architecture of your currently broken install.
Mount the drive containing the broken kernel you want to fix. For example if you have
/, then you will need to do this:
mount /dev/sda3 /mnt
mount /dev/sda1 /mnt/boot
Enter a chroot at your newly mounted mountpoint:
arch-chroot /mnt /bin/bash
Get to pacman's cache directory:
Print a list of all the currently cached linux kernel versions:
Downgrade the kernel! You'll need to replace 'version' with the version you want to downgrade to.
pacman -U linux-version.pkg.tar.xz linux-headers-version.pkg.tar.xz
Get out of that chroot:
Reboot and hold your breath:
Success! Well hopefully at least...
Now stop that pesky kernel from updating until a newer versions comes out that you can test. Change the line:
IgnorePkg = linux linux-headers