stop

# 1) send TERM to Brave's process groups
for pid in $(pgrep -f '(^|/)brave(|-browser)( |$)'); do kill -TERM -"$pid"; done
sleep 1
# 2) hard kill anything left
pkill -KILL -f '(^|/)brave(|-browser)( |$)'

If it keeps coming back (pick what applies):

Flatpak

flatpak kill com.brave.Browser 2>/dev/null

Snap

sudo snap stop brave 2>/dev/null

systemd user scope (GNOME/KDE spawn apps in scopes)

systemctl --user list-units --type=scope | grep -i brave systemctl --user stop app-brave* 2>/dev/null

Auto-start item (prevent re-launch on login/session restore)

mkdir -p ~/.config/autostart-disabled mv ~/.config/autostart/brave*.desktop ~/.config/autostart-disabled/ 2>/dev/null

Then, when you next open Brave: Settings → System → disable “Continue running background apps when Brave is closed.”