corrupted pacman database ?
i can see this kinda often is happening to users regularly often here… caused by powering off in between updating the system… or powerloss…

Backup it automatic with systemd:

Automated Backup In order to keep the backup up-to-date, automation of the aforementioned backup command makes sense.

This can be realized with the tool pakbak-git [AUR] .
Pakbak is a bash script that is triggered by a Systemd service once the contents of the /var/lib/pacman/local directory have been changed.

After installing Pakbak, the destination and the number of backups to be kept in rotation can be set.

sudo nano /etc/pakbak.conf
# Backup the database to this folder 
target_folder = /var/local/pakbak 
# Define how long backups should be kept 
keep_days = 5 
# Define how many backups should be kept 
keep_number = 5

Note: The target directory must be created or already exist.
Environment variables in the path, such as $ HOME will not be processed.
To test whether the bash script works as expected, you can manually initiate the execution with root privileges:

sudo sh/usr/lib/systemd/scripts/pakbak

Then enable the Systemd service, which is the directory /var/lib/pacman/local automatically monitored for changes:

sudo systemctl enable pakbak.path

This is something we could have enabled by default in my opinion, to make Antergos more stable.