Pra nao precisa duplicar código e tals
int[][] offsets = {{-6, 0, 0}, {6, 0, 0}, {0, 0, -6}, {0, 0, 6}};
for( int i = 0; i < offsets.length; i++ )
{
Firework F = (Firework) e.getPlayer().getWorld().spawn(e.getPlayer().getLocation().add(offsets[i][0], offsets[i][1], offsets[i][2]), Firework.class);
FireworkMeta FM = F.getFireworkMeta();
FM.addEffect(FireworkEffect.builder().flicker(false).trail(false).with(Type.BALL).withColor(Color.RED).withFade(Color.BLUE).build());
FM.setPower(this.plugin.getConfig().getInt("Potencia"));
F.setFireworkMeta(FM);
}