==/usr/bin/delugepkill.sh==
#!/bin/bash
pkill -f deluge-gtk
exit

==/usr/lib/systemd/system/deluge-gtk-graceful-kill.service==
[Unit]
Description=kills deluge-gtk gracefully on shutdown
After=network.target

[Service]
Type=oneshot
ExecStart=/bin/true
ExecStop=/usr/bin/delugepkill.sh
TimeoutSec=0
StandardOutput=tty
RemainAfterExit=yes

[Install]
WantedBy=multi-user.target