It's your kernel that got removed. The way
pacman ─ the back-end behind Pamac ─ works for updates is that it first removes the original installed package and then installs the updated package. So it's very likely that you closed Pamac right when it was updating the kernel, which means that it will have removed the kernel binary in
/boot first. So you don't have a kernel, and you don't have a matching
I would suggest booting up from the install medium in live mode, and then in a terminal issue the command...
This will detect your Manjaro installation and will mount the pertinent filesystems, and
chroot into that installation. Then, try resuming the update by issuing the following command...
Hopefully this will complete the update process, but don't presume too early that it would be hanging. Some packages really do take a long time to install ─ e.g. icon sets.
Also, as advice for future reference, it is always recommended not to use any graphical package managers for a system update, but to instead update from a
tty while completely logged out of the GUI environment, and to then reboot immediately afterwards. That way, no shared libraries are in use that are going to be deleted and replaced, and then you stand the least chance of your update/upgrade process getting corrupted.
Addendum: The update/upgrade process also stores all updated packages locally first before it attempts to install them. These packages will be installed under
/var/cache/pacman/pkg, and if you have them all, then you could attempt to install them manually from a
chroot environment as described above.
In your case, I would start with the kernel package. In the
chroot environment, try...
pacman -U exact-name-of-the-package
... first. It may not work, because we've just gone through a change in the way kernels are installed. So you may have to use...
mhwd-kernel -i linux54
Hope any of this helps.