Algo parecido com isto:
#!/bin/bash
for line_num in $(sudo iptables --line-numbers --list PREROUTING -t nat | awk '$7=="to:192.168.2.1:443" {print $1}')
do
# You can't just delete lines here because the line numbers get reordered
# after deletion, which would mean after the first one you're deleting the
# wrong line. Instead put them in a reverse ordered list.
LINES="$line_num $LINES"
done
# Delete the lines, last to first.
for line in $LINES
do
sudo iptables -t nat -D PREROUTING $line
done
unset LINES
Você pode precisar ajustar o número do campo no awk, se não for compatível.