How do you know that it did really freeze? Some updates take a longer time to install, and there’s only so much data that your drive can handle at the same time.
The mistake all of the impatient newbies make, and the result is always the same. 
At the start of the upgrade process, pacman removes the kernels and the initcpios. That is why your system can’t boot anymore if you interrupt the process.
Boot up from the installer medium in live mode, open up a terminal window and type the following two commands… 
sudo su -
manjaro-chroot -a
If necessary, confirm which is your Manjaro installation. Then type the following set of commands, and let each of them finish until they return you to a command prompt…
pacman-mirrors -f 5 && pacman -Syyu
update-grub
sync
exit
systemctl reboot
Bookmark this post for future reference. 