You can't disable tab completion with bungeecord. It's only possible on spigot server. Code (Text): commands: tab-complete: -1 Set tab-complete to -1 to disable.
With code you can try TabCompleteEvent (https://ci.md-5.net/job/BungeeCord/...t/md_5/bungee/api/event/TabCompleteEvent.html) or TabCompleteResponseEvent (https://ci.md-5.net/job/BungeeCord/...ungee/api/event/TabCompleteResponseEvent.html)
also if you just want certain commands to be blocked, use the PlayerCommandSendEvent Example: Code (Text): @EventHandler public void onPlayerTab(PlayerCommandSendEvent e) { List<String> blockedCommands = new ArrayList<>(); blockedCommands.add("gamemode"); blockedCommands.add("pl"); blockedCommands.add("plugins"); e.getCommands().removeAll(blockedCommands); }