REQUIREMENTS:

Create required files:
# install -m 640 -o _pfbadhost -g wheel /dev/null /etc/pf-badhost.txt

Give user "_pfbadhost" doas permission.
 
$ cat /etc/doas.conf
permit root
permit nopass _pfbadhost cmd /sbin/pfctl args -nf /etc/pf.conf
permit nopass _pfbadhost cmd /sbin/pfctl args -t pfbadhost -T replace -f /etc/pf-badhost.txt

Add the following lines to your pf.conf: 

table <pfbadhost> persist file "/etc/pf-badhost.txt"
block in quick on egress from <pfbadhost>
block out quick on egress to <pfbadhost>

For man page

$ man pf-badhost